<PAGE>

                                                                   EXHIBIT 10.20

CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTIONS OF THIS DOCUMENT HAVE
BEEN REDACTED AND HAVE BEEN SEPARATELY FILED WITH THE COMMISSION.

                                   AMENDMENT


     This Amendment is entered into as of March __, 2000 ("Amendment Effective
Date") by and between Support.com, Inc., a Delaware corporation, formerly doing
business as Tioga Systems, Inc. ("SPRT") and At Home Corporation,  doing
business as Excite@Home, a Delaware corporation ("EAH").  This Amendment
modifies the OEM Agreement dated as of July 14, 1999, by and between SPRT and
EAH (the "Agreement") to provide the terms for SPRT's development of an
extension to its Product and for the parties to participate in certain co-
marketing efforts with respect to such extension, in accordance with the terms
of this Amendment.

     1.   Definitions. As used in this Amendment, the following terms have the
          -----------
following meanings.  Capitalized terms used but not defined in this Amendment
have the meanings specified in the Agreement.

               1.1  Product Extension. "Product Extension" means the version of
                    -----------------
the Product that SPRT will develop pursuant to this Amendment.

               1.2  Initial Term. "Initial Term" means the 36-month period
                    ------------
beginning with the Amendment Effective Date.

               1.3  Referred Customers. "Referred Customers" means the customers
                    ------------------
of SPRT that have purchased licenses to the Product Extension and that are
referred to SPRT by EAH in accordance with this Amendment.

               1.4  Net Revenue. "Net Revenue" means the amount collected by
                    -----------
SPRT for SPRT's sale of licenses to the Product Extension to Referred Customers,
less (a) 10% for sales expenses, and (b) any associated freight charges,
insurance and other costs of shipping and handling, taxes and duties.

               1.5  Preliminary Specifications. "Preliminary Specifications"
                    --------------------------
means the preliminary specifications for the Product Extension set forth in
Exhibit A to this Amendment.

               1.6  Renewal Term. "Renewal Term" means the 12-month period after
                    ------------
the Initial Term or Renewal Term, as applicable, of this Amendment.

               1.7  Specifications. The "Specifications" means the
                    --------------
specifications for the Product Extension agreed upon by the parties pursuant to
Section 2.1 of this Amendment.

               1.8  Term. "Term" means the Initial Term and any and all Renewal
                    ----
Terms.

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     2.   Product Extension Development; Ownership.
          ----------------------------------------

               2.1  Within thirty (30) business days following the Amendment
Effective Date, SPRT will submit to EAH a proposal for specifications for the
Product Extension (the "Specifications") to be effective during the twelve (12)
month period following the Amendment Effective Date. Neither the proposed
Specifications nor EAH's proposed modifications will in any event add any new
functionality to the Preliminary Specifications set forth in Exhibit A, but will
provide additional detail associated with each component of the Preliminary
Specifications. Within ten (10) business days following its receipt of the
proposed Specifications, EAH shall notify SPRT that the proposed Specifications
are acceptable or, if they are not acceptable in any respect, then EAH shall
deliver to SPRT reasonable proposed modifications to the proposed
Specifications. Any failure by EAH to notify SPRT that the proposed
Specifications are not acceptable within the time frame set forth above shall be
deemed an acceptance of the proposed Specifications. Within five (5) business
days of receipt of EAH's modifications, SPRT must either accept and incorporate
the proposed modifications or notify EAH that the modifications are not
acceptable. Any failure by SPRT to notify EAH that the modifications are not
acceptable within the time frame set forth above shall be deemed an acceptance
of the modifications. If SPRT properly notifies EAH that the modifications are
not acceptable, then the parties shall negotiate in good faith for a period of
fifteen (15) days using commercially reasonable efforts to mutually agree upon
acceptable Specifications. If after fifteen (15) days the parties are unable to
mutually agree upon acceptable Specifications, then SPRT shall have an
additional five (5) days to either accept EAH's most recent modifications or
immediately terminate the Amendment. Upon the parties reaching agreement as to
the Specifications, they each will execute a copy of an Exhibit setting forth
the Specifications which shall then be appended as Exhibit A to this Amendment.

               2.2  Within thirty (30) business days prior to (a) the first
anniversary of the Amendment Effective Date, and (b) each subsequent six (6)
month period during the Initial Term, SPRT will submit to EAH proposed
specifications ("Enhancement Specifications") with respect to such six (6) month
period for enhancements to the Product Extension ("Enhancements"), for review
and comment. Such Enhancement Specifications and EAH's proposed modifications
thereto (a) will be for feature enhancements to the components and functionality
in the Specifications, (b) will not in any event require a level of development
effort on SPRT's part greater than one half (1/2) of the development effort
required to develop the Product Extension as specified in the Specifications,
and (c) will not be for new components which are not a part of the
Specifications, unless mutually agreed upon. EAH must within ten (10) business
days following its receipt of any such proposed Enhancement Specifications
notify SPRT that the proposal is acceptable or, if not acceptable in any
respect, then EAH must advise SPRT as to any proposed modifications to the
proposed Enhancement Specifications. Any failure by EAH to notify SPRT that the
proposal is not acceptable within the time frame set forth above shall be deemed
an acceptance of the applicable Enhancement Specifications. SPRT will have five
(5) business days following receipt of notice of proposed modifications to
either incorporate the proposed modifications into the proposal or notify EAH of
its rejection of those proposed modifications. Any failure by SPRT to

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notify EAH that the modifications are not acceptable within the time frame set
forth above shall be deemed an acceptance of the modifications. If SPRT properly
notifies EAH that the modifications are not acceptable, then the parties shall
negotiate in good faith for a period of fifteen (15) days using commercially
reasonable efforts to mutually agree upon acceptable Enhancement Specifications.
If after fifteen (15) days the parties are unable to mutually agree upon
acceptable Enhancement Specifications, then SPRT shall have an additional five
(5) days to either accept EAH's most recent modifications or immediately
terminate the Amendment. The foregoing notwithstanding, EAH and SPRT may add any
new features or components to the Enhancement Specification by mutual agreement.
Upon the parties reaching agreement as to the Enhancement Specifications, for
each such six (6) month period, each party will execute a copy of an Exhibit
setting forth the agreed-upon Enhancement Specifications which shall then be
appended as a new Exhibit to this Amendment.

     2.3  Subject to the terms and conditions of this Amendment, SPRT will
develop and deliver the Product Extensions and Enhancements in accordance with
the Specifications and Enhancement Specifications, as applicable, including but
not limited to delivery of such Product Extensions or Enhancements within the
time frame set forth in the applicable Specification or Enhancement
Specification, with allowance for slippage of delivery of any component by an
additional 25% of the number of business days between the acceptance of the
applicable Specification or Enhancement Specification and the time frame set
forth for such component in such applicable Specification or Enhancement
Specification. Upon completion of each Product Extension or Enhancement, SPRT
will provide it to EAH. Within ten (10) days after EAH's receipt of a Product
Extension or Enhancement thereof (which will be provided in executable object
code only), EAH will advise SPRT whether EAH considers the Product Extension or
Enhancement to comply in all material respects with the applicable
Specifications or Enhancement Specifications and will provide the reasons
(including supporting documentation) of any material non-conformities. Any
failure by EAH to notify SPRT that the Product Extension or Enhancements are not
acceptable within the time frame set forth above shall be deemed acknowledgement
by EAH that the Product Extension and/or Enhancements comply in all material
respects with the applicable Specifications or Enhancement Specifications. In
the case that EAH provides SPRT with such notice of any material non-
conformities, SPRT shall have fifteen (15) days to correct the non-conformities
and re-submit the Product Extension or Enhancement to EAH for acceptance. Within
five (5) days after receipt of the corrected Product Extension or Enhancement,
EAH will advise SPRT whether EAH considers the Product Extension or Enhancement
to comply in all material respects with the applicable Specifications or
Enhancement Specifications and will provide the reasons (including supporting
documentation) of any material non-conformities. Any failure by EAH to notify
SPRT that the Product Extension or Enhancements are not acceptable within the
time frame set forth above shall be deemed acknowledgement by EAH that the
Product Extension and/or Enhancements comply in all material respects with the
applicable Specifications or Enhancement Specifications. This process shall
continue until the earlier to occur of: (i) EAH's acknowledgement that the
Product Extension and/or Enhancements comply in all material respects with the
applicable Specifications or Enhancement Specifications, or (ii) 60 days from
the date of the initial notification by EAH of non-conformity of the applicable
Product Extension

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and/or Enhancement. In the event that the Product Extension and/or Enhancements
fail to comply in all material respects with the applicable Specification or
Enhancement Specification after sixty (60) days from the initial notification by
EAH of non-conformity of the applicable Product Extension and/or Enhancement,
EAH may, at its sole discretion, terminate the Amendment.

     2.4  Upon completion of the Product Extension or Enhancement, the Product
Extension or Enhancement will be deemed to be included in the Agreement as the
"Product" and all terms relating thereto shall apply equally to the Product
Extension and Enhancement, including but not limited to the license to EAH set
forth in Section 2.1 through 2.3 and SPRT's ownership set forth in Section 2.4.
Notwithstanding the foregoing, EAH shall not be entitled to sublicense the
Product, Product Extensions or Enhancements, except for the client-side
component (referred to in the Agreement as the Tioga Agent), subject to terms of
the Agreement.

     3.   Referral of Customers.
          ---------------------

               3.1  From time to time, EAH will, during the term of this
Amendment, refer to SPRT certain EAH customers and partners who may be
interested in licensing the Product, Product Extension, and/or Enhancements. EAH
agrees that EAH will position the Product Extension and Enhancements to its
customers and partners as the preferred solution for supporting an end user
internet service. For each such customer or partner that EAH intends to refer to
SPRT, EAH will provide a written notice of such referral, indicating contact
information and other information reasonably requested by SPRT, in the form as
mutually agreed by the parties. Referred Customers shall not include an entity
which (a) Support.com, at the time the contact information is provided, had
already contacted with respect to Support.com products, or (b) is already a
customer of Support.com.

               3.2  SPRT may enter into an agreement with the Referred Customers
at SPRT's own discretion and subject to terms and conditions agreed to with the
Referred Customers. Nothing herein shall obligate SPRT to enter into any
agreement with such Referred Customers. SPRT will have the right to determine in
its sole discretion the price at which SPRT licenses the Product Extension to
Referred Customers.

     4.   Marketing.
          ---------

               4.1  The parties will issue and globally distribute a joint press
release announcing the parties' relationship within 30 calendar days of the
Amendment Effective Date. The parties may, as from time to time they may
mutually agree, issue additional joint press releases regarding successful
development and marketing efforts of the Product Extension and Enhancements, and
regarding the parties' relationship established by this Amendment. Neither party
may otherwise issue any press releases or other public announcements with
respect to this Amendment, without the other party's prior written consent.

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               4.2  The parties will co-brand the Product Extension and the
Enhancements for EAH partners and customers.

     5.   Payments.
          --------

               5.1  EAH agrees to pay SPRT for the development of the Product
Extension the amount of Two Million Seven Hundred Fifty Thousand U.S. Dollars
($2,750,000), payable over a three-year period as set forth in Exhibit B. EAH
shall also pay SPRT for professional services time on the same terms and
conditions as set forth in the Agreement. Such payments shall be in addition
to the License Fees set forth in Section 4.1 of the Agreement.

               5.2  As consideration for EAH's referral of Referred Customers to
SPRT with respect to the Product Extension and/or Enhancements as provided under
this Amendment, and in the event that SPRT actually utilizes the contact
information provided by EAH to license the Product Extension or the Enhancements
to the Referred Customer during the Term, then SPRT will pay EAH [***] percent
([***]%) of SPRT's Net Revenue over $[***] from licensing of the Product
Extension or the Enhancements to such Referred Customers. For the avoidance of
doubt, EAH shall be entitled to receive [***] percent ([***]%) of additional Net
Revenue received by SPRT for Product Extension license fees from such Referred
Customers during the Term.

               5.3  Notwithstanding the foregoing, the parties agree that EAH
will not be entitled to share in revenue received by SPRT from Referred
Customers solely for upgrades to the Product Extension that arise in connection
with or are necessary because of modifications made by SPRT to the Product
Extension, if SPRT charges for such upgrades. If any such upgrade is included as
part of the original sale of the Product Extension license to the Referred
Customer, then EAH will be entitled to its share of the Net Revenue from that
sale pursuant to Section 5.2, other than the portion of the Net Revenue
attributable to the upgrade.

               5.4  EAH's share of the Net Revenues, if any which may accrue
under this Amendment will be payable on a quarterly basis throughout the Term
and will be payable by SPRT within 60 days after the end of each calendar
quarter. Along with each payment, SPRT will provide EAH with a report detailing
the amount of Net Revenues paid hereunder. Such report will include, at a
minimum, Referred Customer name, date of purchase, installation date,
calculation of Net Revenue and EAH's share of the Net Revenue. SPRT will pay in
United States dollars.

     6.   Term and Termination.
          --------------------

               6.1  This Amendment shall take effect as of the Amendment
Effective Date and shall continue in effect, unless and until terminated in
accordance with this Section, during the Term.

               6.2  The term of the Agreement, as set forth in Section 14.1 of
the Agreement, shall be extended to be co-terminus with this Amendment. Section
14.2.1 of

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[***] CONFIDENTIAL MATERIAL REDACTED AND FILED SEPARATELY WITH THE COMMISSION.
<PAGE>

the Agreement shall no longer have any force or effect. Notwithstanding the
foregoing, termination of this Amendment shall not affect the terms and
obligations of the Agreement, and in the event of termination of this Amendment,
the Agreement shall no longer be co-terminus with this Amendment.

               6.3  This Amendment shall terminate automatically upon any
termination of the Agreement.

               6.4  This Amendment may be terminated by either party if the
other party breaches any of its material obligations and fails to cure such
breach within a 30-day period after written notice of such breach.

               6.5  Upon any termination of this Amendment, only those payments
that have accrued pursuant to this Amendment prior to the effective date of
termination will survive and be payable within 60 days of the effective date of
termination, even if longer terms had been provided previously. The provisions
of Section 14.3 through 14.5 of the Agreement shall apply.

     7.   Effect of Amendment; Modification.  In the event of a conflict between
          ---------------------------------
a term or terms of this Amendment and a term or terms of the Agreement, the term
or terms in this Amendment shall control. This Amendment constitutes the entire
agreement between the parties with respect to the subject matter contained
herein, and supersedes all prior oral or written communications between the
parties with respect to the subject matter hereof, but does not supersede the
Agreement unless expressly provided otherwise in this Amendment.  This Amendment
may not be modified, amended or discharged except in writing signed by duly
authorized representatives of both parties.

     8.   Counterparts.  This Amendment may be executed in counterparts, each of
          ------------
which shall be deemed an original, but all of which taken together shall
constitute one and the same instrument.

     IN WITNESS WHEREOF, the parties have executed this Amendment as of the
Amendment Effective Date.


     At Home Corporation                  Support.com, Inc.


     BY: /s/ Lenny Alugas                 BY: /s/ Radha R. Basu
         ---------------------------          ---------------------------

     NAME: Lenny Alugas                   NAME: Radha R. Basu
           -------------------------            -------------------------

     TITLE: V.P. Customer Care            TITLE: CEO & President
            ------------------------             ------------------------

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                                   Exhibit A
                           Preliminary Specifications

The Product Extension shall have the following components or capabilities:
     1.   Integration with [***]: SPRT shall implement integration with [***]
          within six (6) months of acceptance of the Specifications.
     2.   The ability for [***] to gather a set of [***] information from the
          [***] system, and to take appropriate action remotely ("[***] and
          [***]") shall be implemented by SPRT within nine (9) months of
          acceptance of the Specifications.
     3.   Automatic [***] of [***] shall be implemented by SPRT within nine (9)
          months of acceptance of the Specifications.
     4.   A [***] version of the end user agent (the "[***]") shall be
          implemented within twelve (12) months of acceptance of the
          Specifications.


  [***] CONFIDENTIAL MATERIAL REDACTED AND FILED SEPARATELY WITH THE COMMISSION.

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                                   Exhibit B

                                  License Fees

<TABLE>
<CAPTION>
------------------------------------------
Payment         Due Date
------------------------------------------
<S>             <C>
$[***]          August 15, 2000
------------------------------------------
$[***]          November 15, 2000
------------------------------------------
$[***]          February 15, 2001
------------------------------------------
$[***]          May 15, 2001
------------------------------------------
$[***]          August 15, 2001
------------------------------------------
$[***]          November 15, 2001
------------------------------------------
$[***]          February 15, 2002
------------------------------------------
$[***]          May 15, 2002
------------------------------------------
$[***]          August 15, 2002
------------------------------------------
$[***]          November 15, 2002
------------------------------------------
$[***]          February 15, 2003
------------------------------------------
$2,750,000      Total
------------------------------------------
</TABLE>

[***] CONFIDENTIAL MATERIAL REDACTED AND FILED SEPARATELY WITH THE COMMISSION.

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