MSG WC HOLDINGS CORP. STOCKHOLDERS AGREEMENT

Exhibit 4.5

EXECUTION COPY

MSG WC HOLDINGS CORP.

STOCKHOLDERS AGREEMENT

                    THIS STOCKHOLDERS AGREEMENT (this “ Agreement ”) is made as of August 1, 2006 by and among (i) MSG WC Holdings Corp., a Delaware corporation (the “ Company ”), (ii) Welsh, Carson, Anderson & Stowe X, L.P., a Delaware limited partnership (“ WCAS X ”), (iii) WCAS Capital Partners IV, L.P., a Delaware limited partnership (“ CP IV ”), (iv) WCAS Management Corporation, a Delaware corporation (“ WCAS Management Corporation ”), (v) de Nicola Holdings, L.P. (together with WCAS X, CP IV and WCAS Management Corporation, the “ WCAS Investors ”), (vi) the Persons set forth on Schedule A attached hereto as Co-Investors (the “ Co-Investors ”), (vii) the Persons set forth on Schedule A attached hereto as Management Stockholders (the “ Management Stockholders ” and together with the WCAS Investors and the Co-Investors, the “ Initial Stockholders ”), and (viii) each holder of Acquired Securities after the date hereof (individually, an “ Additional Stockholder ” and collectively the “ Additional Stockholders ”, together with the Initial Stockholders, the “ Stockholders ”, and each individually, a “ Stockholder ”). Unless otherwise specified herein, all of the capitalized terms used herein are defined in Section 1 hereof.

                    WHEREAS, the WCAS Investors, the Co-Investors and certain Management Stockholders shall purchase or acquire shares of Common Stock pursuant to a stock purchase agreement between such purchasers and the Company dated as of the date hereof (as such agreement may be amended or otherwise modified from time to time, the “ Purchase Agreement ”) and the Company has granted options to purchase shares of Common Stock to certain Management Stockholders pursuant to option agreements dated as of the date hereof (the “ Option Agreements ”); and

                    WHEREAS, the Company and the Stockholders desire to enter into this Agreement for the purposes, among others, of (i) establishing the composition of the Company’s Board of Directors (the “ Board ”), (ii) assuring continuity in the management and ownership of the Company and (iii) limiting the manner and terms by which the Stockholder Shares may be transferred. The execution and delivery of this Agreement is a condition to each purchaser’s purchase of the Common Stock pursuant to the Purchase Agreement.

                    NOW, THEREFORE, in consideration of the mutual covenants contained herein and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties to this Agreement hereby agree as follows:

                    1. Definitions .

                    “ Acquired Securities ” has the meaning set forth in Section 13 .

                    “ Additional Stockholder ” has the meaning set forth in the preamble.

                    “ Affiliate ” of any particular Person means any other Person controlling, controlled by or under common control with such particular Person, where “control” means the possession,

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directly or indirectly, of the power to direct the management and policies of a Person whether through the ownership of voting securities, contract or otherwise (provided that the Company or any of its Subsidiaries shall not be deemed an Affiliate of any Stockholder).

                    “ Agreement ” has the meaning set forth in the preamble.

                    “ Approved Sale ” has the meaning set forth in Section 9 .

                    “ Attorney-In-Fact ” has the meaning set forth in Section 3 .

                    “ Board ” has the meaning set forth in the preamble.

                    “ Co-Investors ” has the meaning set forth in the preamble.

                    “ Common Stock ” means the Company’s Common Stock, par value $0.01 per share.

                    “ Company ” has the meaning set forth in the preamble.

                    ‘‘ Electing Offeree ” has the meaning set forth in Section 5(a)(ii) .

                    “ Election Notice ” has the meaning set forth in Section 5(a)(ii) .

                    “ Election Period ” has the meaning set forth in Section 5(a)(ii) .

                    “ Equity Securities ” of a Person means, as applicable, (i) any capital stock, membership interests or other share capital of such Person, (ii) any securities of such Person, directly or indirectly convertible into or exchangeable for any capital stock, membership interests or other share capital of such Person or containing any profit participation features with respect to such Person, (iii) any rights or options directly or indirectly to subscribe for or to purchase any capital stock, membership interests, other share capital of such Person or securities containing any profit participation features with respect to such Person or directly or indirectly to subscribe for or to purchase any securities directly or indirectly convertible into or exchangeable for any capital stock, membership interests, other share capital of such Person or securities containing any profit participation features with respect to such Person, (iv) any share appreciation rights, phantom share rights or other similar rights relating to such Person, or (v) any Equity Securities of such Person issued or issuable with respect to the securities referred to in clauses (i) through (iv) above in connection with a combination of shares, recapitalization, merger, consolidation or other reorganization.

                    “ Exempt Transfer ” means any Transfer pursuant to a Public Sale.

                    “ Family Group ” means, with respect to any natural person, such person’s spouse, ancestors and descendants (whether natural or adopted) and any trust or other entity (including a partnership or limited liability company) solely for the benefit of such person and/or such person’s spouse, their respective ancestors and/or descendants.

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                    “ First Refusal Notice ” has the meaning set forth in Section 5(a)(i) .

                     “ Independent Third Party ” means any Person who, immediately prior to the contemplated transaction, (i) does not own in excess of five percent (5%) of the Common Stock on a fully-diluted basis (any Person owning in excess of five percent (5%) of the Common Stock on a fully-diluted basis being referred to herein as a “ 5% Owner ”), (ii) is not an Affiliate of any such 5% Owner or any WCAS Investor, and (iii) is not a member of the Family Group of any such 5% Owner.

                    “ Initial Public Offering ” means an initial public offering of shares of Common Stock registered under the Securities Act.

                    “ Initial Stockholders ” has the meaning set forth in the preamble.

                    “ Management Services Agreement ” means the Management Services Agreement, dated as of the date hereof, by and among the Company, Mobile Services Group, Inc. and WCAS Management Corporation, as such agreement may be amended or otherwise modified from time to time.

                    “ Management Stockholders ” has the meaning set forth in the preamble.

                    “ Maximum Amount ” has the meaning set forth in Section 11 .

                    “ Merger Agreement ” means the Agreement and Plan of Merger, dated as of May 24, 2006, by and among the Company, MSG WC Acquisition Corp., Mobile Services Group and Windward Capital Management, LLC (as stockholder representative), as such agreement may be amended or otherwise modified from time to time.

                    “ Mobile Services Group ” means Mobile Services Group, Inc., a Delaware corporation.

                    “ Mobile Storage Group ” means Mobile Storage Group, Inc., a Delaware corporation.

                    “ MSG WC Intermediary ” means MSG WC Intermediary Co., a Delaware corporation.

                    “ Offered Securities ” has the meaning set forth in Section 10(a) .

                     “ Offerees ” has the meaning set forth in Section 5(a)(i) .

                    “ Option Agreements ” has the meaning set forth in the recitals.

                     “ Option Period ” has the meaning set forth in Section 11 .

                    “ Other Stockholders ” has the meaning set forth in Section 5(b) .

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                    “ Permitted Issuance ” means any issuance of Equity Securities (i) to any director, prospective director, employee, prospective employee or consultant of or to the Company or any of its Subsidiaries pursuant to the Company’s 2006 Stock Option Plan, any other equity incentive plan approved by the Board or any benefit plan approved by the Board not made for the purpose of raising capital, (ii) as a stock dividend or other pro rata distribution or upon any subdivision, split or combination of outstanding Stockholder Shares, (iii) pursuant to an Initial Public Offering, (iv) issued as consideration in any merger, acquisition or joint venture with another business enterprise approved by the Board and the WCAS Majority Holders, not made for the purpose of raising capital, (v) by any Subsidiary of the Company to the Company or to any other Subsidiary of the Company, (vi) to any debt financing source of the Company (so long as such source is not an Affiliate of the Company (excluding CP IV and any of its Affiliates, but including WCAS X) or holder of ten percent (10%) or more of any class of Equity Securities of the Company and such debt financing is approved by the Board), in connection with a so-called “equity-kicker,” and (vii) upon conversion, exchange or redemption of any outstanding convertible or exchangeable securities issued in accordance with the terms of this Agreement and the terms of such securities.

                    “ Permitted Transferee ” has the meaning set forth in Section 5(c) .

                    “ Person ” means an individual, a partnership, a corporation, a limited liability company, an association, a joint stock company, a trust, a joint venture, an unincorporated organization and a governmental entity or any department, agency or political subdivision thereof.

                    “ PR Notice ” has the meaning set forth in Section 10(a) .

                    “ Public Sale ” means any sale of Stockholder Shares to the public pursuant to an effective registration statement or to the public through a broker, dealer or market maker on a securities exchange or in the over-the-counter market pursuant to the provisions of Rule 144 (if such rule is available) adopted under the Securities Act (or any other similar rule or rules then in effect); provided , that a Public Sale shall not include an offering made in connection with a business acquisition or combination pursuant to a registration statement on Form S-4 or any similar form, or an employee benefit plan pursuant to a registration statement on Form S-8 or any similar form.

                    “ Purchase Agreement ” has the meaning set forth in the recitals.

                    “ Purchasing Holder ” has the meaning set forth in Section 10(e) .

                    “ Sale Notice ” has the meaning set forth in Section 5(b) .

                    “ Sale of the Company ” means the sale of the Company, including in one transaction or a series of related transactions, to an Independent Third Party or group of Independent Third Parties pursuant to which such party or parties acquire (i) Equity Securities of the Company representing more than 50% of the voting power of all outstanding voting equity interests (whether by way of merger or consolidation or otherwise), together with the loss by

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WCAS X and its Affiliates, collectively, to elect a majority of the Board, or (ii) all or substantially all of the assets of the Company and its Subsidiaries determined on a consolidated basis.

                    “ SEC ” means the Securities and Exchange Commission.

                    “ Securities Act ” means the Securities Act of 1933, as amended from time to time.

                    “ Selling Investor Stockholder ” has the meaning set forth in Section 5(b) .

                    “ Stockholder Shares ” means (i) any Common Stock issued to or acquired by the Stockholders on or after the date hereof and (ii) any Equity Securities of the Company issued or issuable directly or indirectly with respect to the securities referred to in clause (i) above by way of stock dividend or stock split or in connection with a combination of shares, recapitalization, merger, consolidation or other reorganization. As to any particular shares constituting Stockholder Shares, such shares will cease to be Stockholder Shares when they have been sold in a Public Sale. For purposes of this Agreement, except as otherwise set forth herein, a Person will be deemed to be a holder of Stockholder Shares whenever such Person has the right to acquire directly or indirectly such Stockholder Shares (upon conversion or exercise (without duplication) in connection with a transfer of securities or otherwise, but disregarding any restrictions or limitations upon the exercise of such right), whether or not such acquisition has actually been effected.

                    “ Stockholders ” has the meaning set forth in the preamble.

                    “ Sub Board ” has the meaning set forth in Section 2(a) .

                    “ Sub Debt ” means the indebtedness under the Note Purchase Agreement, dated as of the date hereof, by and among the Company and the purchasers party thereto, as such agreement may be amended or otherwise modified from time to time.

                    “ Subject Shares ” has the meaning set forth in Section 5(a)(i) .

                    “ Subsidiary ” means, with respect to any Person, any corporation, limited liability company, partnership, association or other business entity of which (i) if a corporation, a majority of the total voting power of shares of stock entitled (without regard to the occurrence of any contingency) to vote in the election of directors, managers or trustees thereof is at the time owned or controlled, directly or indirectly, by that Person or one or more of the other Subsidiaries of that Person or a combination thereof, or (ii) if a limited liability company, partnership, association or other business entity, a majority of the limited liability company, partnership or other similar ownership interest thereof is at the time owned or controlled, directly or indirectly, by any Person or one or more Subsidiaries of that Person or a combination thereof. For purposes hereof, a Person or Persons shall be deemed to have a majority ownership interest in a limited liability company, partnership, association or other business entity if such Person or Persons shall be allocated a majority of limited liability company, partnership, association or other business entity gains or losses or shall be or control the managing director or general partner of such limited liability company, partnership, association or other business entity.

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                    “ Transaction Documents ” means (i) this Agreement, (ii) the Merger Agreement, (iii) the Management Services Agreement, (iv) the Registration Agreement, dated as of the date hereof, between the Company and the Stockholders, (v) the Purchase Agreement, (vi) the Amended and Restated Certificate of Incorporation of the Company, (vii) the Employment Agreements, dated as of the date hereof, between the Company and certain Management Stockholders, and (viii) the Option Agreements.

                    “ Transfer ” has the meaning set forth in Section 5 .

                    “ Transferring Stockholder ” has the meaning set forth in Section 5(a)(i) .

                    “ WCAS Directors ” has the meaning set forth in Section 2(a) .

                    “ WCAS Investors ” has the meaning set forth in the preamble.

                    “ WCAS Majority Holders ” means a Stockholder or Stockholders which holds or hold, as the case may be, a majority of the WCAS Shares.

                    “ WCAS Purchase Right ” has the meaning set forth in Section 1 1 .

                    “ WCAS Shares ” means any of the Stockholder Shares held by the WCAS Investors or any of their Affiliates, and any other Person to whom such shares are transferred.

                    “ WCAS X ” has the meaning set forth in the preamble.

                    “ Wholly-Owned Subsidiary ” means, with respect to any Person, a Subsidiary of which all of the outstanding capital stock or other ownership interests are owned by such Person or another Wholly-Owned Subsidiary of such Person.

                    2. Board of Directors .

                    (a) Until the provisions of this Section 2 cease to be effective, each Stockholder shall vote all of his, her or its Stockholder Shares which are voting shares and any other voting securities of the Company over which such Stockholder has voting control and, to the extent permitted by applicable law, shall take all other necessary or desirable actions within his, her or its control (whether in such Stockholder’s capacity as a stockholder, director, member of a board committee or officer of the Company or otherwise, and including, without limitation, attendance at meetings in person or by proxy for purposes of obtaining a quorum and execution of written consents in lieu of meetings, but which shall not include converting or exercising any securities or option convertible or exercisable for voting shares), and the Company shall take all necessary or desirable actions within its control (including, without limitation, calling special board and stockholder meetings), so that:

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                    (b) The Company shall pay the reasonable out-of-pocket expenses incurred by each director in connection with attending the meetings of the Board, any Sub Board and any committee thereof.

                    (c) In the event that any provision of the Company’s bylaws or certificate of incorporation is inconsistent with any provision of this Section 2 , the Stockholders shall take such action as may be necessary to amend any such provision in the Company’s bylaws or certificate of incorporation to remedy such inconsistency.

                    (d) If any party fails to designate a representative to fill a directorship pursuant to the terms of this Section 2 , such directorship shall remain vacant until such party exercises its right to designate a director hereunder.

                    3. Irrevocable Proxy . In order to secure each Stockholder’s obligation to vote his, her or its Stockholder Shares and other voting securities of the Company in accordance with the provisions of Sections 2 and 9 hereof, each Stockholder hereby appoints each of Sanjay Swani and Michael Donovan (each, an “ Attorney-In-Fact ”) as such Stockholder’s true and lawful proxy and attorney-in-fact, with full power of substitution, to (i) vote all of his, her or its Stockholder Shares and other voting securities of the Company for the election and/or removal of directors and all such other matters as expressly provided for in Sections 2 and 9 and (ii) execute any documents in order to effect an Approved Sale (as defined below) as provided for in Section 9 . Each Attorney-In-Fact may exercise the irrevocable proxy granted to him hereunder at any time any Stockholder fails to comply with the provisions of this Agreement. The proxies and powers granted by each Stockholder pursuant to this Section 3 are coupled with an interest and

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are given to secure the performance of each Stockholder’s obligations under this Agreement. Such proxies and powers shall be irrevocable and shall survive the death, incompetency, disability, bankruptcy or dissolution of such Stockholder and the subsequent holders of his, her or its Stockholder Shares.

                    4. Representations and Warranties . Each Stockholder represents and warrants that (i) effective as of the date hereof such Stockholder is the record owner of the number of Stockholder Shares set forth opposite its name on Schedule A attached hereto (assuming all options therefore have become fully vested), free and clear of all liens and encumbrances, (ii) this Agreement has been duly authorized, executed and delivered by such Stockholder and constitutes the valid and binding obligation of such Stockholder, enforceable in accordance with its terms, and (iii) such Stockholder has not granted and is not a party to any proxy, voting trust or other agreement which is inconsistent with, conflicts with or violates any provision of this Agreement. No holder of Stockholder Shares shall grant any proxy or become party to any voting trust or other agreement which is inconsistent with, conflicts with or violates any provision of this Agreement.

                    5. Restrictions on Transfer of Stockholder Shares . Subject to Section 6 , no Management Stockholder or Co-Investor shall sell, transfer, assign, pledge or otherwise dispose of (whether with or without consideration and whether voluntarily or involuntarily or by operation of law) any interest in his, her or its Stockholder Shares (a “ Transfer ”) at any time without the prior written consent of the WCAS Majority Holders (such consent not to be unreasonably withheld in the event that a Management Stockholder intends to make a Transfer of Stockholder Shares in order to address an extreme, demonstrable and extraordinary financial need), except pursuant to the provisions of Section 5(c) (Permitted Transfers), or Section 9 (Sale of the Company) or pursuant to a Public Sale in connection with or following an Initial Public Offering. Each WCAS Investor may Transfer his or its Stockholder Shares, subject to Section 5(b) . No Stockholder shall consummate any Transfer (other than in connection with a Public Sale as contemplated above) until 30 days after the later to occur of the delivery to the Company and the other Stockholders of such Stockholder’s (i) First Refusal Notice or (ii) Sale Notice (if any), unless the parties to the Transfer have been finally determined pursuant to this Section 5 prior to the expiration of such 
30-day period.

                    (a) First Refusal Right .

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                    (b) Tag Along Rights . Subject to Sections 5(c) and 6 , at least fifteen (15) business days prior to any Transfer (other than an Exempt Transfer) by a