<PAGE>

                                    [LETTERHEAD]


                                    April 1, 1997

Joseph Mazin, President & CEO
PERFECTDATA CORPORATION
110 West Easy Street
Simi Valley, California 93065-1689

Re: Modification of Financing Arrangements
    --------------------------------------

Dear Mr. Mazin:

Reference is made to that certain Loan Agreement dated as of November 2, 
1995, entered into between PERFECTDATA CORPORATION ("Borrower") and 
MANUFACTURERS BANK ("Bank"), together with any and all amendments, 
modifications, riders and attachments thereto (collectively, the "Loan 
Agreement"), governing certain financial accommodations which Bank has 
extended to Borrower. All capitalized terms used in this letter shall have 
the meanings given to them in the Loan Agreement, unless specifically defined 
herein.

Bank has reviewed the financing arrangements provided to Borrower under the 
Loan Agreement and all other related loan documents, and is willing to modify 
the Loan Agreement, subject to the following terms and conditions:

1. Section 6.2(a) is modified by deleting the word "monthly", and replacing 
it with the word "quarterly".

Except as expressly amended above, the Loan Documents shall remain unchanged 
and in full force and effect.

Kindly cause Borrower to indicate their acceptance of this Agreement by 
signing the enclosed copy where indicated and returning it to us. This offer 
shall expire at 5:00 p.m. on April 18, 1997, unless prior to that time we 
have received such copy duly executed.

                                         Very truly yours,
                                         MANUFACTURERS BANK,

                                         Cris Castellini
                                         Assistant Vice President

                                         AGREED AND ACCEPTED:

Dated: April 9, 1997                     PERFECTDATA CORPORATION,
       --------------------              a California corporation

                                         By: /s/ Joseph Mazin
                                            -----------------------------------
                                            Joseph Mazin

                                         Title: President & CEO
                                               --------------------------------


                                         By: /s/ Irene J. Marino
                                            -----------------------------------
                                            Irene J. Marino

                                         Title: V.P. Finance & Corp. Secretary
                                               --------------------------------

                                   Page 1 of 1
                                  Exhibit 10.66


<PAGE>

                                    [LETTERHEAD]


                                    October 24, 1996

Mr. Joseph Mazin
PERFECTDATA CORPORATION
110 West Easy Street
Simi Valley, California 93065-1689

Re: Modification of Financing Arrangements
    --------------------------------------

Dear Mr. Mazin:

Reference is made to (i) that certain Loan Agreement dated as of November 2, 
1995, entered into between PERFECTDATA CORPORATION ("Borrower") and 
MANUFACTURERS BANK ("Bank"), together with any and all alterations, 
amendments, changes, extensions, modifications, riders, and supplements 
thereto (collectively, the "Loan Agreement"), (ii) that certain promissory 
note in the original principal amount of One Million Dollars ($1,000,000.00) 
dated August 2, 1992 and executed by Borrower in favor of Bank (the "Note"), 
and (iii) any and all documents executed in connection with the Loan 
Agreement (which documents, together with the Loan Agreement and the Note, 
are collectively referred to as the "Loan Documents"), pursuant to which Bank 
has extended certain financial accommodations to Borrower. Any and all 
capitalized terms used herein shall have the meanings ascribed to them in the 
Loan Agreement, unless specifically defined below.

At your request we have reviewed the financing arrangements which we have 
provided to Borrower under the Loan Documents and are willing to modify the 
Loan Agreement and the Note as set forth below:

1. Section 6.2(a) of the Loan Agreement is deleted and replaced with the 
following:

   6.2(a) FINANCIAL PROJECTIONS FOR BORROWER. Deliver to Bank not less than 
ninety (90) days before the end of each of Borrower's fiscal years, monthly 
financial projections for Borrower including balance sheets, income 
statements, cash flow projections and letter of credit usage projections, 
for the next succeeding fiscal year, prepared by Borrower.

2. Section 6.3(f) is added to the Loan Agreement as follows:

   6.3(f) LIQUIDITY. (i) At all times maintain Net Liquid Assets in an amount 
not less than Three Hundred Thousand Dollars ($300,000.00) and (ii) deliver 
to Bank, within thirty (30) days after the end of each calendar quarter, 
written evidence of compliance with this covenant satisfactory to Bank. As 
used in this Section, "Net Liquid Assets" means cash, bank deposits, 
marketable securities, mutual funds, municipal bonds and municipal bond 
funds, wherever located or maintained, net of the aggregate amount of all 
indebtedness secured by any lien or encumbrance of any nature whatsoever 
affecting any of such assets.

3. Note is modified by extending its maturity date and the last date for 
obtaining advances thereunder from October 31, 1996, to August 31, 1997. 
Availability of credit remains subject to any other conditions contained in 
the Note.

Except as expressly amended above, the Loan Documents shall remain unchanged 
and in full force and effect. Kindly cause Borrower to indicate their 
acceptance of this Agreement by signing the enclosed copy where indicated and 
returning it to us. This offer shall expire at 5:00 p.m. on October 31, 
1996, unless prior to that time we have received such copy duly executed.


                                         Very truly yours,
                                         MANUFACTURERS BANK,

                                         /s/ Karen Stein
                                         Karen Stein
                                         Vice President

                                         AGREED AND ACCEPTED:

Dated: Oct 25, 1996                  PERFECTDATA CORPORATION,
       --------------------              a California corporation

                                         By: /s/ Joseph Mazin
                                            -----------------------------------
                                            Joseph Mazin

                                         Title: President & CEO
                                               --------------------------------


                                         By: /s/ Irene J. Marino
                                            -----------------------------------
                                            Irene J. Marino

                                         Title: V.P. Finance & Corp. Secretary
                                               --------------------------------

                                   Page 1 of 1
                                  Exhibit 10.66