<PAGE>
 
                                                                   EXHIBIT 10(N)

NationsBank
NationsBank of Texas, N.A.
________________________________________________________________________________



                                FOURTH AMENDMENT
                                       TO
                        FINANCING AND SECURITY AGREEMENT


     This Fourth Amendment to Financing and Security Agreement is executed and
entered into by COMPUCOM SYSTEMS, INC. ("Borrower") and NATIONSBANK OF TEXAS,
N.A. ("Lender"), effective as of the 1st day of October, 1995, as follows:


                                    RECITALS
                                    --------

     Borrower and Lender are parties to the certain Financing and Security
     Agreement dated effective as of August 4, 1993, as amended by (i) the First
     Amendment to Financing and Security Agreement dated effective as of March
     31, 1994 (the "First Amendment"), (ii) the Second Amendment to Financing
     and Security Agreement dated effective as of December 12, 1994 and (iii)
     the Third Amendment to Financing and Security Agreement dated effective as
     of April 26, 1995 (collectively the "Financing and Security Agreement").

     Borrower and Lender have agreed to amend the Financing and Security
     Agreement as provided herein.

     NOW THEREFORE, premises considered, for value received, Borrower and Lender
hereby agree as follows:

     1.   Each of the following definitions contained in ARTICLE I
("DEFINITIONS") of the Financing and Security Agreement hereby is amended to
read in its entirety as follows:

     1.68 "LIBOR FIXED RATE" means the Adjusted LIBOR Rate plus one and one-half
     percent (1.50%) per annum.

     "1.13  "CONTRACT RATE" means, on any day, a floating annual rate of
     interest calculated on the basis of actual days elapsed but computed as if
     each year consists of 360 days, equal to the sum of the Prime Rate
     effective as of the first day of the calendar month in which such day falls
     plus zero percent (0.00%).  Upon written notification to Borrower at any
     time when any Event of Default exists, the Contract Rate otherwise
     applicable hereunder shall automatically increase by an additional two
     percent (2.0%) per annum, beginning on the effective date specified in such
     written notice (which shall be on or after the date on which any such Event
     of Default shall have first occurred) and continuing thereafter for so long
     as any such Event of Default remains uncured or until Lender may agree
     otherwise.

     2.   Paragraph 3.8 of the Financing and Security Agreement hereby is
amended such that, in the fourth sentence thereof, the phrase "two (2) Business
Days" shall be deemed to read "one (1) Business Day".

     3.   The following items shall be delivered to Lender prior to or
simultaneously with execution and delivery of this Fourth Amendment:

          (a)  A certificate signed by the corporate secretary of Borrower (i)
     certifying to Lender that its Certificate of Incorporation and Bylaws have
     not been amended since Borrower's certification thereof under Secretary's
     Certificate dated May 9, 1995 previously delivered to Lender, and that the
     officers of Borrower specified therein are duly elected, qualified and
     acting in the capacities therein stated, as of the effective date hereof
     and (ii) attaching and certifying resolutions duly adopted by the board of
     directors of Borrower, or a duly authorized executive committee thereof,
     authorizing this Fourth Amendment and the transactions evidenced hereby,
     and authorizing and directing one or more named officers of Borrower to
     execute and deliver this Fourth Amendment, and all related documentation
     required by Lender, on behalf of Borrower, which certificate shall be in
     form satisfactory to Lender;

          (b)  Amendments to Participation Agreements as may be required by
     Lender in connection with this Fourth Amendment, in form satisfactory to
     Lender;

          (c)  Such other documentation as Lender may reasonably require in
     connection with the Financing and Security Agreement or this Fourth
     Amendment.

     5.   In consideration of this Fourth Amendment, Borrower represents to
Lender that (i) no Event of Default, or other event or condition which would be
the subject of a required notice under paragraph 6.14 of the Financing and
Security Agreement, is in existence as of the effective date hereof, (ii) each
of
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the representations and warranties contained in the following paragraphs of the
Financing and Security Agreement are true and correct as of the effective date
of this Fourth Amendment: paragraphs 3.3, paragraph 3.4, and paragraph 5.1
through paragraph 5.18.  Borrower hereby ratifies and confirms the Financing and
Security Agreement as being and continuing in full force and effect, as amended
by this Fourth Amendment.

     6.   This Fourth Amendment (i) shall be deemed effective prospectively as
of the effective date specified in the preamble, (ii) contains the entire
agreement among the parties and may not be amended or modified except in writing
signed by all parties, (iii) shall be governed and construed according to the
laws of the State of Texas and (iv) may be executed in any number of
counterparts, each of which shall be valid as an original and all of which shall
be one and the same agreement.  A telecopy of any executed counterpart shall be
deemed valid as an original.

     THIS WRITTEN AGREEMENT REPRESENTS THE FINAL AGREEMENT BETWEEN THE PARTIES
     -------------------------------------------------------------------------
     AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR
     --------------------------------------------------------------------
     SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES.  THERE ARE NO UNWRITTEN ORAL
     -----------------------------------------------------------------------
     AGREEMENTS BETWEEN THE PARTIES.
     ------------------------------ 

     EXECUTED as of the effective date specified in the preamble.

                                    NATIONSBANK OF TEXAS, N.A.


                                    By:  /s/ Sally Pershica
                                         ------------------
                                         Sally Pershica
                                         Senior Vice President

                                    COMPUCOM SYSTEMS, INC.


                                    By:  /s/ Robert J. Boutin
                                         --------------------
                                         Robert J. Boutin
                                         Senior Vice President, Finance
                                         and Chief Financial Officer



                            CONSENT BY PARTICIPANTS
                            -----------------------

     Each of the undersigned consents to Borrower's and Lender's execution of
the above Fourth Amendment to Financing and Security Agreement:


BARNETT BANK OF TAMPA                       MIDLANTIC BANK, N.A.             
                                                                             
                                                                             
By:______________________________           By:______________________________
Name:____________________________           Name:____________________________
Title:___________________________           Title:___________________________
                                                                             
NATIONAL CANADA FINANCE CORP.               UNION BANK                       
                                                                             
                                                                             
By:______________________________           By:______________________________
Name:____________________________           Name:____________________________
Title:___________________________           Title:___________________________
                                                                             
                                                                             
SANWA BUSINESS CREDIT CORPORATION           THE DAIWA BANK, LTD.             
                                                                             
                                                                             
By:______________________________           By:______________________________ 
Name:____________________________           Name:____________________________ 
Title:___________________________           Title:___________________________ 
                                                                             
                                                                             
                                            By:______________________________
                                            Name:____________________________
                                            Title:___________________________ 

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THE STATE OF TEXAS           (S)

COUNTY OF DALLAS             (S)

     BEFORE ME, the undersigned authority, on this day personally appeared Sally
Pershica, known to me to be the person and officer whose name is subscribed to 
the foregoing instrument, and acknowledged to me that the same was the act of 
the said NATIONSBANK OF TEXAS, N.A., and was executed for the purposes and 
consideration therein expressed and in the capacity therein stated.

     GIVEN UNDER MY HAND AND SEAL OF OFFICE this the 6th day of December 1995.

                                             /s/ Paula N. Potcinske
                                             ----------------------------------
                                             NOTARY PUBLIC, STATE OF TEXAS

My Commission Expires:                                                          

---------------------                        ----------------------------------
                                             (Printed Name of Notary)

                                             [NOTARY SEAL APPEARS HERE]




THE STATE OF TEXAS           (S)

COUNTY OF DALLAS             (S)

     BEFORE ME, the undersigned authority, on this day personally appeared 
Robert J. Boutin, known to me to be the person and officer whose name is
subscribed to the foregoing instrument, and acknowledged to me that the same was
the act of the said COMPUCOM SYSTEMS, INC., and was executed for the purposes
and consideration therein expressed and in the capacity therein stated.

     GIVEN UNDER MY HAND AND SEAL OF OFFICE this the 4th day of October 1995.

                                             /s/ M. Patricia Tarkington
                                             ----------------------------------
                                             NOTARY PUBLIC, STATE OF TEXAS

My Commission Expires:
      4/1/98                                 M. Patricia Tarkington   
---------------------                        ----------------------------------
                                             (Printed Name of Notary)

                                             [NOTARY SEAL APPEARS HERE]

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