Amendment No. 3 to Second Amended and Restated Credit and Security Agreement and related Documents

[EXECUTION COPY]

Exhibit 10.1

PC CONNECTION, INC.

Route 101A (730 Milford Road)

Merrimack, NH 03054

Dated as of: October 15, 2007

RBS Citizens, National Association

28 State Street

Boston, MA 02109

Ladies and Gentlemen:

We refer to the Second Amended and Restated Credit and Security Agreement, dated as of June 29, 2005 (as amended by that certain Amendment No. 1, dated as of August 12, 2005, and Amendment No. 2, dated as of January 3, 2007, the “Credit Agreement”), by and among PC Connection, Inc., a Delaware corporation (the “Borrower”), certain subsidiary guarantors party thereto, and RBS Citizens, National Association, successor by merger to Citizens Bank of Massachusetts, as the lender (in such capacity, the “Lender”) and agent (together with its successors and assigns in such capacity, the “Agent”).

We have requested that the Agent and Lender agree to make certain amendments to the Credit Agreement and we have been advised that the Agent and Lender are prepared and would be pleased to make the amendments to the Credit Agreement upon the terms and subject to the conditions set forth below.

Accordingly, in consideration of the premises, promises, mutual covenants and agreements set forth below, and fully intending to be legally bound hereby, the parties hereto agree as follows:

ARTICLE I

AMENDMENTS TO CREDIT AGREEMENT

Effective as of October 15, 2007 (the “Amendment Date”), and subject to the fulfillment of the conditions contained in Article II of this Amendment, the Credit Agreement is hereby amended in each of the following respects:

(a)    The term, “Documents” shall, wherever used in the Credit Agreement or Other Documents, be deemed to also mean and include this Amendment. All capitalized terms used but not defined herein shall have the meanings given to such terms in the Credit Agreement.

(b)    The Credit Agreement is amended as follows:

(i)     Section 1.2 . Section 1.2 of the Credit Agreement is amended by amending and restating the following defined terms therein to read in their entirety as follows:

“ Applicable Margin ” shall mean, for each of the Base Rate, the Eurodollar Rate, the LIBOR Advantage Rate and the Commitment Fee, the per annum percentage set forth below opposite the corresponding Funded Debt Ratio for the preceding fiscal quarter, as determined by the Compliance Certificate and the corresponding financial statements delivered to the Agent by the Borrower pursuant to Section 9.8 hereof:

; provided , that if the Borrower shall fail to deliver a Compliance Certificate and the corresponding financial statements within the time required by such Section 9.8, then the Applicable Margin for each of the Base Rate, the Eurodollar Rate, the LIBOR Advantage Rate and the Commitment Fee shall be the respective Applicable Margin set forth in Level I for the period commencing on the first calendar day of the fiscal quarter following the fiscal quarter for which such financial statements are to be delivered pursuant to Section 9.8 until such Compliance Certificate is delivered. Subject to the last clause of the immediately preceding sentence, any increase or reduction in the Applicable Margin shall be effective on the first calendar day of the month following the month in which the Agent receives the Compliance Certificate and the corresponding financial statements pursuant to Section 9.8, accompanied in the case of any reduction in the Applicable Margin by a certificate of the Borrower requesting such reduction. In the event that the Borrower’s annual financial statements indicate that the Applicable Margin as applied in any fiscal quarter therein was lower than it should have been due to an error in the quarterly financial statements and/or

2

Compliance Certificate delivered by the Borrower, then the amount of additional interest that would have been due for each such fiscal quarter if the correct Applicable Margin had been applied shall be paid by the Borrower to the Agent on demand.

“ Permitted Acquisitions ” shall mean the acquisition by Borrower of all or a substantial portion of the assets or capital stock of any Person (the “Acquired Entity”) engaged in a business substantially similar to the Line of Business, which acquisition satisfies all of the following criteria: (a) the aggregate consideration paid or payable by Borrower in connection with such acquisition (including earn out payments, seller paper or deferred purchase price payments) shall not exceed $15,000,000; (b) Borrower causes any new Subsidiary acquired or formed in connection with such Permitted Acquisition to comply with all of the provisions of Section 6.10; and (c) no Default or Event of Default shall have occurred or result from such Acquisition (to be demonstrated through delivery by the Borrower of a pro forma Compliance Certificate to Agent satisfactory to the Agent).

(ii)     Section 1.2 . Section 1.2 of the Credit Agreement is further amended by adding the following new defined terms in appropriate alphabetical order therein:

“ LA Interest Payment Date ” means, initially, November 15, 2007, and thereafter the day of each succeeding month which numerically corresponds to such date or, if a month does not contain a day that numerically corresponds to such date, the LA Interest Payment Date shall be the last day of such month.

“ LA Interest Period ” means, with respect to any LIBOR Advantage Rate Loan, the period commencing on (and including) October 15, 2007 (the “Start Date”) and ending on (but excluding) the date which numerically corresponds to such date one month later, and thereafter, each one month period ending on the day of such month that numerically corresponds to the Start Date. If a LA Interest Period is to end in a month for which there is no day which numerically corresponds to the Start Date, the LA Interest Period will end on the last day of such month.

“ LIBOR Advantage Loan ” shall mean a Revolving Advance for which the applicable rate of interest is based upon the LIBOR Advantage Rate.

“ LIBOR Advantage Rate ” means, relative to any LA Interest Period, the offered rate for delivery in two London Banking Days of deposits of U.S. Dollars for a term coextensive with the LA Interest Period which the British Bankers’ Association fixes as its LIBOR rate as of 11:00 a.m. London time on the day on which such LA Interest Period commences. If the first day of any LA Interest Period is not a day which is both a (i) Business Day, and (ii) a London Banking Day, the LIBOR Advantage Rate shall be determined by reference to the next preceding day which is both a Business Day and a London Banking Day. If for any reason the LIBOR Advantage Rate is unavailable and/or the Agent is unable

3

to determine the LIBOR Advantage Rate for any LA Interest Period, the Agent may, at its discretion, either: (a) select a replacement index based on the arithmetic mean of the quotations, if any, of the interbank offered rate by first class banks in London or New York for deposits with comparable maturities or (b) accrue interest at a rate per annum equal to the Domestic Rate as of the first day of any LA Interest Period for which the LIBOR Advantage Rate is unavailable or cannot be determined.

“ London Banking Day ” means any day on which dealings in US dollar deposits are transacted in the London interbank market.

“ Type ” means a LIBOR Rate Loan, a Domestic Rate Loan or a LIBOR Advantage Loan, as the case may be.

(iii)    Section 2.1.     Section 2.1 of the Credit Agreement is amended and restated to read in its entirety as follows:

“ 2.1   Revolving Advances .

(a)    Subject to the terms and conditions set forth in this Agreement including, without limitation, Section 2.1(b), each Lender, severally and not jointly, will make Revolving Advances to Borrower in aggregate amounts outstanding at any time equal to such Lender’s Commitment Percentage of the lesser of (x) the Maximum Advance Amount less (i) the aggregate amount of outstanding Letters of Credit and (ii) the Foreign Exchange Sub-Limit, or (y) an amount equal to the sum of:

The amount derived from (x) the sum of Sections 2.1(a)(y)(i) and (ii) minus (y) the sum of Sections 2.1(a)(y)(iii) and (iv) at any time and from time to time shall be referred to as the “Formula Amount”. The Revolving Advances shall be evidenced by one or more secured promissory notes (collectively, the

4

“Revolving Credit Note”) substantially in the form attached hereto as Exhibit 2.1(a) .]

(b)     Discretionary Rights . The Advance Rates may be increased or decreased by Agent at any time and from time to time in the exercise of its reasonable discretion. Borrower consents to any such increases or decreases and acknowledges that decreasing the Advance Rates may limit or restrict Advances requested by Borrower.”

Section 2.2 .   Section 2.2 of the Credit Agreement is amended and restated to read in its entirety as follows:

“ 2.2     Procedure for Revolving Advance Borrowing; Eurodollar Rate Loans ; LIBOR Advantage Loans .

(a)    With respect to Revolving Advances, Borrower may notify Agent prior to 12:00 noon (Boston time) at least one Business Day prior to the date of the proposed borrowing of Borrower’s request to incur a Revolving Advance hereunder. Each request for a Revolving Advance shall, unless Borrower requests a loan of another Type, be deemed to be a request for a LIBOR Advantage Loan. The amount of any Revolving Advance request shall be a minimum of $100,000. Should any amount required to be paid as interest hereunder, or as fees or other charges under this Agreement or any other agreement with Agent or Lenders, or with respect to any other Obligation, become due, same shall be deemed a request for a Revolving Advance as of the date such payment is due, in the amount required to pay in full such interest, fee, charge or Obligation under this Agreement or any other agreement with Agent or Lenders, and such request shall be irrevocable.

(b)    Notwithstanding the provisions of subsection (a) above, with respect to all Advances, in the event Borrower desires to obtain a Eurodollar Rate Loan, Borrower must notify Agent prior to 10:00 a.m. (Boston time) at least two (2) Business Days’ prior to the date of the proposed borrowing specifying (i) the date of the proposed borrowing (which shall be a Business Day), (ii) the type of borrowing and the amount on the date of such Advance to be borrowed, which amount shall be a minimum of $1,000,000 and an integral multiple of $1,000,000, and (iii) the duration of the first Interest Period therefor. Interest Periods for Eurodollar Rate Loans shall be for one, two, three, four or six months; provided, if an Interest Period would end on a day that is not a Business Day, it shall end on the next succeeding Business Day unless such day falls in the next succeeding calendar month in which case the Interest Period shall end on the next preceding Business Day. No Eurodollar Rate Loan or LIBOR Advantage Loan shall be made available to Borrower during the continuance of a Default or an Event of Default.

(c)    Each Interest Period of a Eurodollar Rate Loan shall commence on the date such Eurodollar Rate Loan is made and shall end on such date as

5

Borrower may elect as set forth in subsection (b)(iii) above provided that the exact length of each Interest Period shall be determined in accordance with the practice of the interbank market for offshore Dollar deposits and no Interest Period shall end after the last day of the Term. Borrower shall elect the initial Interest Period applicable to a Eurodollar Rate Loan by its notice of borrowing given to Agent pursuant to Section 2.2(b) or by its notice of conversion given to Agent pursuant to Section 2.2(d), as the case may be. Borrower shall elect the duration of each succeeding Interest Period by giving irrevocable written notice to Agent of such duration not less than three (3) Business Days prior to the last day of the then current Interest Period applicable to such Eurodollar Rate Loan. If Agent does not receive timely notice of the Interest Period elected by Borrower, Borrower shall be deemed to have elected to convert to a LIBOR Advantage Loan subject to Section 2.2(d) herein below.

(d)    Borrower may, subject to the notice requirements set forth below, on any Business Day convert any Revolving Advance of one Type into a Revolving Advance of another Type in the same aggregate principal amount, provided that no Revolving Advance may be converted into a LIBOR Advantage Loan or Eurodollar Rate Loan if any Default or Event of Default shall have occurred and be continuing, and provided , further , that no Eurodollar Rate Loan may be converted into a Loan of another Type or of a different Interest Period except on the last day of the Interest Period applicable thereto. If Borrower desires to convert a Revolving Advance, Borrower shall give prior written notice to agent by 10:00 a.m. (Boston time) (i) in the case of converting to a Eurodollar Rate Loan or a LIBOR Advantage Loan, not less than two (2) nor more than five (5) Business Days’ prior to the date of conversion and (ii) in the case of converting to a Domestic Rate Loan, not less than one Business Day prior to the date of conversion, which notice shall specify the proposed date of such conversion (which in the case of Eurodollar Rate Loans shall be on the last day of the Interest Period applicable thereto), the Revolving Advance and amount to be converted (which, in the case of conversions to Eurodollar Rate Loans or LIBOR Advantage Loans shall be in an aggregate minimum amount of $1,000,000 and integral multiples of $1,000,000), and, in the case of conversions to Eurodollar Rate Loans, the Interest Period applicable thereto. After giving effect to any borrowing or each such conversion, there shall not be outstanding more than four (4) Eurodollar Rate Loans, in the aggregate.

(e)    If any Default or Event of Default shall have occurred and be continuing, at the option of the Required Lenders, each Eurodollar Rate Loan and LIBOR Advantage Loan shall be deemed to convert to a Domestic Rate Loan on the last day of the Interest Period or LA Interest Period, as applicable, in effect with respect thereto.

(f)    Borrower may prepay Domestic Rate Loans and LIBOR Advantage Loans in whole at any time or in part from time to time with accrued interest on the principal being prepaid to the date of such repayment. Upon not less than two (2) Business Days’ prior written notice, Borrower may (subject to

6

Sections 3.1 and 13.1 hereof) prepay Eurodollar Rate Loans in whole at any time or in part from time to time with accrued interest on the principal being prepaid to the date of such repayment. Borrower shall specify the date of prepayment of Advances which are Eurodollar Rate Loans and the amount of such prepayment. In the event that any prepayment of a Eurodollar Rate Loan is required or permitted on a date other than the last Business Day of the then current Interest Period with respect thereto, Borrower shall indemnify Agent and Lenders therefor in accordance with Section 2.2(g) hereof.

(g)    Borrower shall indemnify Agent and Lenders and hold Agent and Lenders harmless from and against any and all losses or expenses that Agent and Lenders may sustain or incur as a consequence of any prepayment, conversion of or any default, whether voluntary or involuntary by Borrower in the payment of the principal of or interest on any Eurodollar Rate Loan or failure by Borrower to complete a borrowing of, a prepayment of or conversion of or to a Eurodollar Rate Loan after notice thereof has been given, including, but not limited to, any interest payable by Agent or the Lenders to other lenders of funds obtained by them in order to make or maintain their Eurodollar Rate Loans hereunder. A certificate or statement as to any additional amounts payable pursuant to the foregoing sentence (which shall include upon the written request of the Borrower a reasonably detailed calculation and description) submitted by Agent or any Lender to Borrower shall be conclusive absent manifest error.

(h)    Notwithstanding any other provision hereof, if any applicable law, treaty, regulation or directive, or any change therein or in the interpretation or application thereof, shall make it unlawful for any Lender (for purposes of this subsection (h), the term “Lender” shall include any Lender and the office or branch where Lender or any corporation or bank controlling such Lender makes or maintains Eurodollar Rate Loans hereof) to make or maintain its Eurodollar Rate Loans, the obligation of Lenders to make Eurodollar Rate Loans hereunder shall automatically be cancelled and Borrower shall, if any affected Eurodollar Rate Loans are then outstanding, promptly upon request from Agent, either pay all such affected Eurodollar Rate Loans in full or convert such affected Eurodollar Rate Loans into loans of another type. If any such payment or conversion of any Eurodollar Rate Loan is made on a day that is not the last day of the Interest Period applicable to such Eurodollar Rate Loan, Borrower shall pay Agent, upon Agent’s request, such amount or amounts as may be necessary to compensate Lenders for any loss or expense sustained or incurred by Lenders in respect of such Eurodollar Rate Loan as a result of such payment or conversion, including (but not limited to) any interest or other amounts payable by Agent or the Lenders to other lenders of funds obtained by Lenders in order to make or maintain such Eurodollar Rate Loan. A certificate or statement as to any additional amounts payable pursuant to the foregoing sentence (which shall include upon the written request of the Borrower a reasonably detailed calculation and description) submitted by Lenders to Borrower shall be conclusive absent manifest error.”

7

Section 2.19 .     Section 2.19 of the Credit Agreement is amended and restated to read in its entirety as follows:

“ 2.19     Increase of Commitments . At any time during the Term, the Borrower shall have the right, but not the obligation, upon no less than ninety (90) days written notice to the Agent, to increase the Maximum Advance Amount by an aggregate amount not to exceed $30,000,000 under terms and conditions identical to those of the Revolving Advances, such additional amounts to be provided by the then existing Lenders or such other persons who become Lenders in connection therewith; provided that no such existing Lender shall be obligated to provide any such Advance in connection with the increase in the Maximum Advance Amount, and this section shall not be deemed a commitment by any Lender to increase such Maximum Advance Amount.”

(v)     Section 3.1 .     Section 3.1 of the Credit Agreement is amended and restated to read in its entirety as follows:

“ 3.1     Interest . Interest on Advances shall be payable in arrears, on the first day of each month with respect to Domestic Rate Loans, on each LA Interest Payment Date with respect to LIBOR Advantage Loans and, with respect to Eurodollar Rate Loans, at the end of each Interest Period or, for Eurodollar Rate Loans with an Interest Period in excess of three months, at the earlier of (a) each three months on the anniversary date of the commencement of such Eurodollar Rate Loan and (b) the end of the Interest Period. Interest charges shall be computed on the actual principal amount of Advances outstanding during the month at a rate per annum equal to (w) with respect to LIBOR Advantage Loans, the LIBOR Advantage Rate plus the Applicable Margin thereto, (x) with respect to Domestic Rate Loans, the Base Rate plus the Applicable Margin thereto and (y) with respect to Eurodollar Rate Loans, the Eurodollar Rate plus the Applicable Margin thereto (as applicable, the “Contract Interest Rate”). Whenever, subsequent to the date of this Agreement, the Base Rate is increased or dec