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                                                                  Exhibit 10.20


        THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
        AMENDED, OR ANY STATE SECURITIES LAWS, AND MAY NOT BE OFFERED OR SOLD,
        UNLESS IT HAS BEEN REGISTERED UNDER SUCH ACT AND APPLICABLE STATE
        SECURITIES LAWS OR UNLESS AN EXEMPTION FROM REGISTRATION IS AVAILABLE.


                     SUBORDINATED PROMISSORY NOTE DUE 2010

$59,100,000.00                                                   August 7, 1997
                                                             New York, New York

        DECISIONONE HOLDINGS CORP., a Delaware corporation (the "BORROWER"),
for value received, hereby promises to pay, in lawful money of the United
States in immediately available funds, to DecisionOne Corporation, a Delaware
corporation, or its registered assigns (the "HOLDER"), at 50 East Swedesford
Road, Frazer, Pennsylvania 19355, or such other place as the Holder may
designate from time to time, on August 31, 2010, the principal sum of Fiftynine
Million One Hundred Thousand Dollars (the "PRINCIPAL AMOUNT"). Interest
(computed on the basis of a 360-day year of twelve 30-day months) will be paid
in cash or accrued at the rate of 8.25% per annum on the Principal Amount from
time to time remaining unpaid hereon, semi-annually on November 30 and May 31 of
each year (commencing on November 30, 1997) until said Principal Amount shall
be paid in full.


        The Borrower hereby waives presentment, demand, protest or notice of
any kind in connection with this Note.

        This Note and the indebtedness evidenced hereby is subordinated to the
prior payment in full of all other indebtedness for borrowed money of the
Borrower (but not trade payables arising in the ordinary course of business),
whether currently existing or hereinafter incurred (any such indebtedness, the
"SENIOR DEBT"). No payment of principal, interest or other amounts in respect
of the indebtedness evidenced hereby shall be made at any time at which there
exists any default or event of default in respect of any Senior Debt. Upon any
dissolution, winding up, liquidation or reorganization of the Borrower, all
principal, interest and other amounts payable in respect of any Senior Debt
shall be paid in full before any payment is made in respect of the indebtedness


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evidenced hereby. In the event that any payment shall be made in respect of the
indebtedness evidenced hereby in contravention of the terms hereof, such
payment shall be held in trust by the recipients thereof for the benefit of,
and shall be paid forthwith over and delivered to, the holders of the Senior
Debt for application pro rata to the payment of all Senior Debt to the extent
necessary to pay such Senior Debt in full.

        Subject to the foregoing, the Borrower may, at its option, pay the
Principal Amount in whole at any time without the Holder's prior demand, and
upon final payment in full of the Principal Amount and any accrued interest
thereon, this Note shall immediately be deemed cancelled and of no further
force or effect without any further action on the part of the Borrower.

        This Note is registered on the books of the Borrower and is
transferable only by surrenders hereof at the principal office of the Borrower
duly endorsed or accompanied by a written instrument of transfer duly executed
by the Holder or its attorney duly authorized in writing. Payment of or on
account of principal and interest on the Note shall be made only to or upon the
order in writing of the Holder.

        THIS NOTE SHALL BE CONSTRUED IN ACCORDANCE WITH AND SHALL BE GOVERNED
BY THE INTERNAL LAWS (AND NOT THE CONFLICTS LAWS) OF THE STATE OF NEW YORK.


                                        DECISIONONE HOLDINGS CORP.

                                        By: /s/ Thomas J. Fitzpatrick
                                           --------------------------
                                           Name:  Thomas J. Fitzpatrick
                                           Title: Vice President and
                                                  Chief Financial Officer 




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