Document:

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                                                                   EXHIBIT 10.37

                                  WENTWORTH LLC
                                CORPORATE CENTER
                                  WEST BAY ROAD
                          GRAND CAYMAN, CAYMAN ISLANDS

                                                          April 13, 2000

ESAT, Inc.
Bldg. G
16520 Harbor Boulevard
Fountain Valley, California 92708
Attention: President

                                           Re:    ESAT, Inc.  (the "Company")

Gentlemen:

        We write with reference to the Transaction Documents for the Series C 6%
Convertible Preferred Stock dated December 29, 1999.

        This will confirm that with respect to the Transaction Documents, and in
consideration of the issuance and sale of the Series D Convertible Preferred
Stock to Wentworth LLC, the Company and Wentworth LLC agree that:

        1. The parties have mutually modified the provisions of that certain
additional agreement with respect to the sale of additional shares of Common
Stock to provide that the Company agrees to deliver one or more Additional
Financing Notices for a minimum of $10,000,000 on or before July 13, 2001, and
the shares to be issued shall be the subject of a separate Registration
Statement.

        2. The Initial Required Effective Date under Paragraph 2(a)(i) of the
Registration Rights Agreement is amended to a date which is not later than the
earlier of (x) five days after notice by the SEC, or (y) May 31, 2000, and
Section 5(b) of the Registration Rights Agreement shall be amended to read as
follows:

        "The Buyer acknowledges that the Company either intends to issue shares
        or has already issued shares as of the date of this agreement pursuant
        to its advisory agreement with Grayson & Associates (the "Other
        Registrable Shares")."

        3. We hereby consent that an amended Certificate of Designation for
Series C Convertible Preferred Stock shall be filed substantially in the form of
Exhibit 1 to this letter.

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        Please indicate your agreement with the foregoing by executing a
countersigned copy of this letter and returning the same to our attention,
whereupon effective immediately thereafter this letter shall become a legally
valid and binding agreement between the Purchasers and the Company.

                                            Sincerely,

                                            WENTWORTH LLC

                                            By: /s/ Navigator Management, Ltd.
                                               ---------------------------------

Agreed and accepted
April 13, 2000

ESAT, INC.

By: /s/ Michael C. Palmer
   ----------------------
    Name: Michael C. Palmer
    Title: Chief Executive Officer<PAGE>   1

                                                                  EXHIBIT 10.12i

                           WAIVER AND AMENDMENT NO. 9

                                       TO

                                CREDIT AGREEMENT

                  This WAIVER AND AMENDMENT NO. 9 to CREDIT AGREEMENT (the
"Amendment"), dated as of June 1, 2000, is entered into by and among American
Architectural Products Corporation, a Delaware corporation ("AAPC"), Eagle &
Taylor Company, a Delaware corporation, Forte, Inc., an Ohio corporation,
Western Insulated Glass, Co., an Arizona corporation, Thermetic Glass, Inc., a
Delaware corporation, Binnings Building Products, Inc., a Delaware corporation,
Danvid Window Company, a Delaware corporation, Modern Window Corporation,
formerly known as Modern Window Acquisition Corporation, a Delaware corporation,
American Glassmith, Inc., formerly known as American Glassmith Acquisition
Corporation, a Delaware corporation, VinylSource, Inc., a Delaware corporation,
American Weather-Seal Company, formerly known as Weather-Seal Acquisition
Corporation, a Delaware corporation, Eagle Window & Door Center, Inc., a
Delaware corporation, Denver Window Company, formerly known as Denver Window
Acquisition Corporation, a Delaware corporation, AAPC One Acquisition
Corporation, a Delaware corporation, and AAPC Two Acquisition Corporation, a
Delaware corporation (the "Borrowers"), the financial institutions party hereto
(the "Lenders"), and BankBoston, N.A., in its capacity as contractual
representative for itself and the other Lenders (the "Agent") under that certain
Credit Agreement, dated as of June 9, 1998, as amended, by and among the
Borrowers, the Lenders and the Agent (the "Credit Agreement"). Defined terms
used herein and not otherwise defined herein shall have the meanings given to
them in the Credit Agreement.

                                   WITNESSETH

                  WHEREAS, AAPC has informed the Agent and the Lenders that it
does not anticipate making an interest payment on June 1, 2000 under the Senior
Notes that is due and payable on such date (the "June 1, 2000 Interest
Payment");

                  WHEREAS, with respect to fiscal year 1999, the Borrowers
anticipate receipt of a qualified "going concern" opinion (the "1999 Going
Concern Opinion") from independent third-party accountants retained by the
Borrowers;

                  WHEREAS, each of the failure to make the June 1, 2000 Interest
Payment and the Borrowers' receipt of the 1999 Going Concern Opinion constitutes
a Default or an Event of Default under the Credit Agreement (together, the "June
1, 2000 Defaults");

                  WHEREAS, the Borrowers have requested that the Lenders and the
Agent provide a limited waiver under the Credit Agreement with respect to the
June 1, 2000 Defaults;

                  WHEREAS, the Borrower has also requested that the Lenders and
the Agent provide limited waivers under the Credit Agreement with respect to
Defaults under SECTIONS

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7.3(S), 7.4(A), and 7.4(C) of the Credit Agreement (collectively, the "Financial
Covenant Defaults");

                  WHEREAS, the Borrowers also wish to amend the Credit Agreement
in certain respects;

                  WHEREAS, the Lenders and the Agent are willing to provide the
requested limited waivers and amend the Credit Agreement on the terms and
conditions set forth herein;

                  NOW, THEREFORE, in consideration of the premises set forth
above, the terms and conditions contained herein, and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
Borrowers, the Agent and the Lenders hereby agree as follows:

         1. LIMITED WAIVER FOR JUNE 1, 2000 DEFAULTS; LIMITED WAIVER FOR
FINANCIAL COVENANT DEFAULTS. (a) Effective as of the date hereof, as expressly
limited hereby and subject to the satisfaction of the conditions precedent set
forth in SECTION 3 below, the Lenders and the Agent hereby agree to waive those
requirements related to the June 1, 2000 Defaults set forth in the Credit
Agreement, which, if not waived, would cause the June 1, 2000 Defaults to
constitute Defaults or Events of Default, including, without limitation, the
requirements of SECTION 7.1(a)(iii) and SECTION 8.1(E) of the Credit Agreement
as such Sections relate to the June 1, 2000 Defaults; PROVIDED, HOWEVER, that in
the event any Person exercises any rights or remedies under or in connection
with the Senior Notes as a result of AAPC's failure to make the June 1, 2000
Interest Payment, the waiver granted hereunder with respect to such failure
shall immediately be null, void, and terminated, the June 1, 2000 Default
related thereto shall constitute a Default under the Credit Agreement for so
long as such failure continues, and the Agent and the Lenders shall be entitled
to exercise all rights and remedies available to them under the Credit Agreement
subsequent to the occurrence of a Default.

         (b) Effective as of the date hereof, as expressly limited hereby and
subject to the satisfaction of the conditions precedent set forth in Section 3
below, the Lenders and the Agent hereby agree to waive the Financial Covenant
Defaults as follows: (i) the Lenders and the Agent hereby waive the Default
under SECTION 7.3(S) for the period beginning April 15, 2000 and ending June 1,
2000, (ii) the Lenders and the Agent hereby waive the Default under SECTION
7.4(A) for the fiscal quarter ending December 31, 1999, and (iii) the Lenders
and the Agent hereby waive the Default under SECTION 7.4(C) for the fiscal
quarter ending December 31, 1999. Notwithstanding the foregoing or anything else
to the contrary contained herein, the waivers granted hereunder shall in no way
terminate, limit, or otherwise affect the terms of or AAPC's obligations under
the letter, dated as of May 19, 2000, delivered by AAPC to the Agent.

         2. AMENDMENT. Effective as of the date first above written and subject
to the satisfaction of the conditions precedent set forth in SECTION 3 below,
the Credit Agreement shall be and hereby is amended as follows:

                  (a) SECTION 2.2 of the Credit Agreement is hereby amended to
insert the following immediately at the end thereof:

                                       2
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                  "Notwithstanding anything to the contrary contained in this
SECTION 2.2 or elsewhere in the Credit Agreement or any document, instrument or
agreement executed and delivered in connection therewith, no Eurodollar Rate
Loan or Eurodollar Rate Advance shall be requested by any Borrower or be made by
the Agent or the Lender on or after June 1, 2000. Any Eurodollar Rate Loan or
Eurodollar Rate Advance already in existence on June 1, 2000 shall be repaid in
full on the last day of the Interest Period related thereto or shall be
converted to a Floating Rate Loan or Floating Rate Advance on the last day of
such Interest Period, as applicable."

                  (b) SECTION 7.1(A)(v) of the Credit Agreement is hereby
amended to insert the following immediately at the end thereof:

                  "Notwithstanding anything to the contrary contained in this
SECTION 7.1(A)(v) or elsewhere in the Credit Agreement or any document,
instrument or agreement executed and delivered in connection therewith, upon the
Agent's request and at the Agent's discretion, the Borrowers shall deliver
Borrowing Base Certificates to the Agent more frequently than monthly, with such
frequency determined by the Agent."

         3. CONDITIONS OF EFFECTIVENESS. This Amendment shall become effective
and be deemed effective as of the date hereof, if, and only if the Agent shall
have received:

         (i) three (3) duly executed originals of this Amendment from the
Borrowers and the Required Lenders, and

         (ii) the Agent shall have received a fee equal to $125,000 in
immediately available funds.

         4. REPRESENTATIONS AND WARRANTIES OF THE BORROWERS. Each Borrower
hereby represents and warrants as follows:

                  (a) The Credit Agreement to which each Borrower is a party as
previously executed constitutes the legal, valid and binding obligation of such
Borrower and is enforceable against such Borrower in accordance with its terms.

                  (b) Upon the effectiveness of this Amendment, each Borrower
hereby (i) represents that no Default or Unmatured Default exists under the
terms of the Credit Agreement, (ii) reaffirms all covenants, representations and
warranties made in the Credit Agreement, and (iii) agrees that all such
covenants, representations and warranties shall be deemed to have been remade as
of the effective date of this Amendment. The execution, delivery and
effectiveness of this Amendment shall not, except as expressly provided herein,
operate as a waiver of any right, power, or remedy of the Lenders or the Agent
under the Credit Agreement or any related document, instrument or agreement. The
Agent and the Lenders expressly reserve all of their rights and remedies,
including the right to institute enforcement actions in consequence of any
existing Defaults or Events of Default not waived hereunder at any time without
further notice, under the Credit Agreement, all other documents, instruments and
agreement executed in connection therewith, and applicable law.

         5. EFFECT ON THE CREDIT AGREEMENT.

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<PAGE>   4

                  (a) Upon the effectiveness of this Amendment, on and after the
date hereof, each reference in the Credit Agreement to "this Agreement,"
"hereunder," "hereof," "herein" or words of like import shall mean and be a
reference to such Credit Agreement, as amended hereby.

                  (b) Except as specifically amended above, the Credit Agreement
and all other documents, instruments and agreements executed and/or delivered in
connection therewith shall remain in full force and effect, and are hereby
ratified and confirmed.

                  (c) The execution, delivery and effectiveness of this
Amendment shall neither, except as expressly provided herein, operate as a
waiver of any right, power or remedy of the Lenders or the Agent, nor constitute
a waiver of any provision of the Credit Agreement or any other documents,
instruments and agreements executed and/or delivered in connection therewith.

         6. COSTS AND EXPENSES. The Borrowers agree to pay all reasonable costs,
fees and out-of-pocket expenses (including attorneys' fees and expenses charged
to the Agent) incurred by the Agent and the Lenders in connection with the
preparation, arrangement, execution and enforcement of this Amendment.

         7. GOVERNING LAW. This Amendment shall be governed by and construed in
accordance with the laws (including, without limitation, Section 735 ILCS
105/5-1 et seq. but otherwise without regard to the conflict of law provisions)
of the State of Illinois.

         8. HEADINGS. Section headings in this Amendment are included herein for
convenience of reference only and shall not constitute a part of this Amendment
for any other purpose.

         9. COUNTERPARTS. This Amendment may be executed by one or more of the
parties to the Amendment on any number of separate counterparts and all of said
counterparts taken together shall be deemed to constitute one and the same
instrument.

         10. NO STRICT CONSTRUCTION. The parties hereto have participated
jointly in the negotiation and drafting of this Amendment. In the event an
ambiguity or question of intent or interpretation arises, this Amendment shall
be construed as if drafted jointly by the parties hereto and no presumption or
burden of proof shall arise favoring or disfavoring any party by virtue of the
authorship of any provisions of this Amendment.

The remainder of this page is intentionally blank.

                                       4

<PAGE>   5

                  IN WITNESS WHEREOF, this Waiver and Amendment No. 9 has been
duly executed as of the day and year first above written.

<TABLE>
<S>                                                         <C>
AMERICAN ARCHITECTURAL                                      BANKBOSTON, N.A., individually and as Agent
PRODUCTS CORPORATION

EAGLE AND TAYLOR COMPANY                                    By: /S/ EDWARD BARTKOWSKI
                                                                ---------------------------------------
                                                            Name: Edward Bartkowski
FORTE, INC.                                                 Title: Authorized Officer

WESTERN INSULATED GLASS, CO.

THERMETIC GLASS, INC.

BINNINGS BUILDING PRODUCTS, INC.

DANVID WINDOW COMPANY

MODERN WINDOW CORPORATION

AMERICAN GLASSMITH, INC.

VINYLSOURCE, INC.

AMERICAN WEATHER-SEAL
COMPANY

EAGLE WINDOW & DOOR CENTER, INC.

DENVER WINDOW COMPANY

AAPC ONE ACQUISITION CORPORATION

AAPC TWO ACQUISITION CORPORATION

By: /S/ WILLIAM T. HULL
    ------------------------------------
(on behalf of the above-listed parties)
         Name:  William T. Hull
         Title:  Chief Financial Officer
</TABLE>

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