<PAGE>
                                                                   Exhibit 10.42


         SECOND AMENDMENT TO SECOND AMENDED AND RESTATED LOAN AGREEMENT

     This SECOND AMENDMENT TO SECOND AMENDED AND RESTATED LOAN AGREEMENT (this
"Amendment"), dated as of March 31, 2006, is entered into by and among DYNAMICS
RESEARCH CORPORATION, a Massachusetts corporation, DRC INTERNATIONAL
CORPORATION, a Massachusetts corporation, and H.J. FORD ASSOCIATES, INC., a
Delaware corporation, with their principal executive offices at 60 Frontage
Road, Andover, Massachusetts (hereinafter, individually and collectively,
jointly and severally, the "Borrowers") and BROWN BROTHERS HARRIMAN & CO., as
administrative agent (when acting in that capacity, the "Administrative Agent")
and as a lender, TD BANKNORTH, N.A, FORMERLY KNOWN AS BANKNORTH, N.A., as
documentation agent and as a lender, KEYBANK NATIONAL ASSOCIATION, as
co-syndication agent and as a lender, and BANK OF AMERICA, N.A., SUCCESSOR BY
MERGER TO FLEET NATIONAL BANK, a Bank of America company as co-syndication agent
and as a lender (hereinafter, individually and collectively, the "Lenders").

     WHEREAS, the Borrowers, the Administrative Agent and the Lenders are
parties to that certain Second Amended and Restated Loan Agreement dated as of
September 1, 2004 (as may be amended and in effect from time to time, the
"Credit Agreement"), pursuant to which the Lenders, upon certain terms and
conditions, agreed to make loans to, and to issue letters of credit for the
benefit of, the Borrowers;

     WHEREAS, the Borrowers have requested that the Administrative Agent and the
Lenders acknowledge and agree that a Collateral Release Event has occurred,
notwithstanding the fact that the Borrowers' have not technically satisfied the
conditions therefor, for the purpose of releasing and discharging the Collateral
Interests granted pursuant to the Security Documents; and

     WHEREAS, the Administrative Agent and the Lenders have agreed, on the terms
and subject to the conditions set forth herein, to such acknowledgement,
agreement and release.

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto hereby agree as
follows:

1.   Defined Terms. Capitalized terms which are used herein without definition
     and which are defined in the Credit Agreement shall have the same meanings
     herein as in the Credit Agreement.

2.   Amendment and Release. Notwithstanding the provisions of Section 5.3 of the
     Credit Agreement, the Borrowers, the Administrative Agent and the Lenders
     acknowledge and agree that effective as of the date of this Amendment, a
     Collateral Release Event shall be deemed to have occurred for the purposes
     of the following Security Documents, and that such Security Documents (and
     all of the provisions contained therein, including the security interests
     granted by the Borrowers to the Administrative Agent for the ratable
     benefit of the Lenders pursuant thereto) are hereby terminated, and shall
     have no further force or effect:

          (i)  Security Agreement dated September 1, 2004 executed by the
               Borrowers, Andrulis Corporation and Impact Innovations Group LLC
               in favor of the Lenders (See Section 2c(iv) of this Security
               Agreement);

          (ii) Patent and Patent Application Security Agreement dated September
               1, 2004 executed by Dynamics Research Corporation in favor of the
               Lenders (See Section 10 of this Patent and Patent Application
               Security Agreement);

         (iii) Section 10 of the Trademark and Trademark Application Security
               Agreement dated September 1, 2004 executed by Dynamics Research
               Corporation in favor of the Lenders (See Section 10 of this
               Patent and Patent Application Security Agreement);

          (iv) Pledge Agreement dated September 1, 2004 executed by Dynamics
               Research Corporation in favor of the Lenders (See Section 13 of
               this Pledge Agreement);


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          (v)  Pledge Agreement dated September 1, 2004 executed by DRC
               International Corporation in favor of the Lenders (See Section 13
               of this Pledge Agreement);

          (vi) Pledge Agreement dated September 1, 2004 executed by H.J. Ford
               Associates, Inc. in favor of the Lenders (See Section 13 of this
               Pledge Agreement);

         (vii) Pledge Agreement dated September 1, 2004 executed by Andrulis
               Corporation in favor of the Lenders (See Section 13 of this
               Pledge Agreement); and

        (viii) Pledge Agreement dated September 1, 2004 executed by Impact
               Innovations Group LLC in favor of the Lenders (See Section 13 of
               this Pledge Agreement).

     To the extent necessary to effectuate the foregoing termination and
     release, the Administrative Agent will promptly execute and deliver to the
     Lead Borrower (or its counsel), at the Borrowers' expense, any and all
     releases, UCC-3 termination statements and other documents and instruments
     which are reasonably necessary and appropriate in order to terminate of
     record the Collateral Interest granted to the Administrative Agent pursuant
     to the foregoing Security Documents.

3.   Representations and Warranties. The Borrowers hereby represent and warrant
     to the Lenders as follows:

          a.   The execution and delivery of this Amendment by the Borrowers and
               the performance by the Borrowers of their obligations and
               agreements under this Amendment and the Credit Agreement as
               amended hereby are within the corporate authority of the
               Borrowers, have been duly authorized by all necessary corporate
               proceedings on behalf of the Borrowers and do not and will not
               contravene any provision of law, statute, rule or regulation to
               which the Borrowers are subject or the Borrowers' charters, other
               incorporation papers, by-laws or any stock provision or any
               amendment thereof or of any agreement or other instrument binding
               upon the Borrowers.

          b.   This Amendment and the Credit Agreement as modified hereby
               constitute legal, valid and binding obligations of the Borrowers,
               enforceable against the Borrowers in accordance with their
               respective terms, except as limited by bankruptcy, insolvency,
               reorganization, moratorium or other laws relating to or affecting
               generally the enforcement of creditors' rights in general, and by
               general principles of equity (regardless of whether such
               enforceability is considered in a proceeding in equity or at
               law).

          c.   No approval or consent of, or filing with, any governmental
               agency or authority is required to make valid and legally binding
               the execution, delivery or performance by the Borrowers of this
               Amendment or the Credit Agreement as modified hereby.

4.   Waiver of Claims: The Borrowers hereby acknowledge and agree that they do
     not have any offsets, defenses, claims, or counterclaims against the
     Lenders or any of their respective officers, directors, employees,
     affiliates, attorneys, representatives, predecessors, successors, or
     assigns with respect to the Credit Agreement or any of the other Loan
     Documents, the Liabilities, or otherwise, and that if the Borrowers now
     have, or ever did have, any such offsets, defenses, claims, or
     counterclaims against the Lenders or any of their respective officers,
     directors, employees, attorneys, representatives, predecessors, successors,
     or assigns, whether known or unknown, at law or in equity, from the
     beginning of the world through this date and through the time of execution
     of this Amendment, all of them are hereby expressly WAIVED, and the
     Borrowers hereby RELEASE the Lenders and their respective officers,
     directors, employees, affiliates, attorneys, representatives, predecessors,
     successors, and assigns from any liability therefor.

5.   Miscellaneous Provisions.


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          a.   Except as otherwise expressly provided by this Amendment, all of
               the terms, conditions and provisions of the Credit Agreement
               shall remain the same. It is declared and agreed by each of the
               parties hereto that the Credit Agreement, as modified hereby,
               shall continue in full force and effect, and that this Amendment
               and the Credit Agreement shall be read and construed as one
               instrument.

          b.   This Amendment is intended to take effect as an agreement under
               seal and shall be construed according to and governed by the laws
               of the Commonwealth of Massachusetts.

          c.   This Amendment may be executed in any number of counterparts, but
               all such counterparts shall together constitute but one
               instrument. In making proof of this Amendment it shall not be
               necessary to produce or account for more than one counterpart
               signed by each party hereto by and against which enforcement
               hereof is sought.

                  (remainder of page intentionally left blank)


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     IN WITNESS WHEREOF, the parties hereto have executed this Amendment as of
the date first written above.


                                                  BORROWERS:


                                                  DYNAMICS RESEARCH CORPORATION


                                                  By /s/ David Keleher
                                                    ---------------------------
                                                  Name: DAVID KELEHER
                                                       ------------------------
                                                  Title: SR. VP & CFO
                                                        -----------------------


                                                  DRC INTERNATIONAL CORPORATION


                                                  By /s/ David Keleher
                                                    ---------------------------
                                                  Name: DAVID KELEHER
                                                       ------------------------
                                                  Title: VP
                                                        -----------------------


                                                  H.J. FORD ASSOCIATES, INC.


                                                  By /s/ David Keleher
                                                    ---------------------------
                                                  Name: DAVID KELEHER
                                                       ------------------------
                                                  Title: VP & CFO
                                                        -----------------------


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ACKNOWLEDGED AND AGREED
-----------------------

LENDERS:

BROWN BROTHERS HARRIMAN & CO.
("ADMINISTRATIVE AGENT AND LENDER")



By /s/ John D. Rogers
  ----------------------------
Name: John D. Rogers
     -------------------------
Title: Senior Vice President
      ------------------------



TD BANKNORTH, N.A., FORMERLY KNOWN AS BANKNORTH, N.A.
("DOCUMENTATION AGENT AND LENDER")



By /s/ Jeffrey R. Westling
  ----------------------------
Name: Jeffrey R. Westling
     -------------------------
Title: Senior Vice President
      ------------------------




KEYBANK NATIONAL ASSOCIATION
("CO-SYNDICATION AGENT AND LENDER")



By /s/ Daniel DiMarco
  -----------------------------
Name: Daniel DiMarco
     --------------------------
Title: Assistant Vice President
      -------------------------




BANK OF AMERICA, N.A., SUCCESSOR BY
MERGER TO FLEET NATIONAL BANK,
A BANK OF AMERICA COMPANY
("CO-SYNDICATION AGENT AND LENDER")




By /s/ Jean S. Manthorne
  ----------------------------
Name: Jean S. Manthorne
     -------------------------
Title: Senior Vice President
      ------------------------





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