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                                                                   EXHIBIT 10.43

                              ASSIGNMENT AGREEMENT

         This Assignment Agreement dated March 26, 2003 by and among Arnos Corp.
("Arnos" or "Lender"), Edgemont Limited Partnership ("Edgemont LP"), NEG
Operating LLC ("Operating LLC") and National Energy Group, Inc. ("NEG" or
"Assignor") shall act to assign that certain Loan Agreement dated August 29,
1996 among NEG as Borrower, NEG-OK Inc. and Boomer Marketing Corporation as
Guarantors AND Bank One Texas, N.A. and Credit Lyonnais, New York Branch, as
amended on October 31, 1996, March 7, 1997, May 12, 1997, August 21, 1997,
August 1, 2001 and December 15, 2001 (the "Loan Agreement"). Edgemont LP and
Operating LLC may sometimes be referred to herein collectively as "Assignees"
and individually as "Assignee".

                                   WITNESSETH:

         WHEREAS, pursuant to that certain Assignment Agreement between Bank One
Texas, N.A., Credit Lyonnais, New York Branch, and Arnos Corp. dated December
22, 1998, Arnos became successor-in-interest and acquired all of the right,
title and interest in and to the Loan Agreement held by Bank One Texas, N.A. and
Credit Lyonnais, New York Branch; and

         WHEREAS, Arnos, NEG, Edgemont LP and Operating LLC have agreed that all
of NEG's right, title and interest in and to the Loan Agreement shall be
assigned to Assignees.

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

         1. Assignor hereby assigns and transfers to Assignees, and Assignees
hereby assume from Assignor all of Assignor's right, title and interest in and
to the Loan Agreement.

         2. Assignor hereby represents and warrants that it has the full right,
power and authority to transfer and assign its interest in the Loan Agreement,
subject to the consent of holders of NEG's senior note obligations.

         3. Each Assignee hereby represents and warrants that it has the full
right, power and authority to enter into and perform the obligations pursuant to
this Assignment Agreement and the Loan Agreement.

         4. This Assignment Agreement is effective of the date first written
above, and each Assignee is hereby deemed a party to the Loan Agreement with all
the rights and obligations of a Borrower thereunder. As of the effective date,
Assignor hereby relinquishes all its rights under the Loan Agreement and is
hereby released from any and all of its obligations pursuant thereto.

         5. Each of Lender, Assignor and Assignees shall take such action and
execute and deliver to the other all such documents and instruments as may be
necessary to implement this Assignment Agreement and to consummate the
transactions contemplated hereby.

         6. By its execution and delivery of this Assignment Agreement, each of
Arnos, NEG, Edgemont LP and Operating LLC (i) agrees to the assignment of the
Loan Agreement as contemplated herein, and (ii) waives compliance with Section
27(a)(1), (2) and (4) of the Loan Agreement.

         7. By its execution and delivery of this Assignment Agreement, each of
Arnos, High River Limited Partnership and High Coast Limited Partnership, as the
holders of NEG's senior note obligations, hereby consents to the assignment of
the Loan Agreement as contemplated herein.


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         8. THIS ASSIGNMENT AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO THE
PRINCIPALS OF CONFLICT OF LAWS.

         IN WITNESS WHEREOF, the parties have caused this Assignment Agreement
to be executed and delivered on the date first written above.

                                  Arnos Corp., as Lender and a Noteholder

                                  By: /s/ EDWARD E. MATTNER
                                     ------------------------------------------
                                  Name: Edward E. Mattner
                                  Its:  Vice President

                                  National Energy Group, Inc., as Assignor

                                  By: /s/ BOB G. ALEXANDER
                                     ------------------------------------------
                                  Name:  Bob G. Alexander
                                  Its:   President & Chief Executive Officer

                                  NEG Operating LLC, as Assignee
                                  By: NEG Holding LLC, Sole Member
                                  By: Gascon Partners, Managing Member
                                  By: Cigas Corp., Managing General Member

                                  By: /s/ EDWARD E. MATTNER
                                     ------------------------------------------
                                  Name: Edward E. Mattner
                                  Its:  President

                                  Edgemont Limited Partnership, as Assignee
                                  By: GP of Delaware LLC, its General Partner

                                  By: /s/ EDWARD E. MATTNER
                                     ------------------------------------------
                                  Name: Edward E. Mattner
                                  Its:  Manager



          CONSENTED TO BY NOTEHOLDERS:

          High River Limited Partnership
          By:  Barberry Corp., Its General Partner

          By: /s/ EDWARD E. MATTNER
             --------------------------------------------
          Name: Edward E. Mattner
          Its:  Authorized Signatory

          High Coast Limited Partnership
          By:  Beckton Corp. its General Partner

          By: /s/ EDWARD E. MATTNER
             --------------------------------------------
          Name: Edward E. Mattner
          Its:  Authorized Signatory