<PAGE>

                                                                   Exhibit 10.13


August 1, 1999

PERSONAL & CONFIDENTIAL
Mark Pincus
1572 Shrader Street
San Francisco, CA  94117

Dear Mark:

On behalf of Tioga Systems, Inc. (the "Company" or "Tioga") I am pleased to
offer you the position of Chairman and Founder of the Company.  The terms of
your employment relationship with the company are as set forth below and as
approved by the Company's Board of Directors.

1. Position:  You will be the Chairman and Founder of the Company, reporting to
   the Board of Directors. As such, you will have such responsibilities as
   determined by the Board of Directors.

2. Base Salary and Performance Bonus: You will be paid a base salary of $15,000
   per month.  Your salary will be payable in accordance with the Company's
   standard payroll policies (subject to normal required withholding). You will
   receive a vacation and benefit package similar to that provided for all other
   executive level employees.

3. Stock Options: Subject to the approval of the Board of Directors of the
   Company, you will be granted (i) an option to purchase 250,000 shares of
   Common Stock of the Company at an exercise price per share equivalent to the
   fair market value as determined by the Board of Directors at the July 21,
   1999 Board meeting and which will vest monthly at the rate of 1/12 per month
   and, (ii) an option to purchase 250,000 shares of Common Stock of the Company
   at an exercise price per share equivalent to the fair market value as
   determined by the Board of Directors at the July 21, 1999 Board meeting and
   which will vest monthly at 1/48 per month. Your options will be granted under
   the Tioga Systems, Inc. 1998 Option Plan, in accordance with and subject to
   each term of the Company's standard form of option agreement.

4. At-Will Employment: You will be an employee-at-will, meaning that either you
   or the Company can terminate your employment relationship at any time, for
   any reason, with or without Cause, and with or without notice. You agree to
   devote substantially all of your business time and attention to the Company.
   Nevertheless, you shall be permitted to serve as a member of the board of
   directors of Brightlight as well as such other boards of directors of for-
   profit and not-for-profit organizations as the Board may reasonable approve.
<PAGE>

5.   Termination of Employment:

5.1  In the event your employment is terminated by the Company with or without
     Cause, as defined herein, or you resign with or without Good Reason, as
     defined herein, you will be entitled to payment of (i) accrued salary,
     benefits and reimbursable expenses owing to you through the date of such
     termination, and (ii) the bonus you earned for the Fiscal Year preceding
     the date of your termination if it has not been paid as of the date of your
     termination.

5.2  If your employment is terminated by the Company, for any reason other than
     for Cause, or is terminated by you for Good Reason, in addition to the
     payments provided for in Section 5.1, you will be entitled to receive a
     severance package consisting of (i) your base monthly salary, paid as
     though you were still employed by the Company for a period of 12 months in
     installments, subject to appropriate deductions, (ii) continued
     participation in all benefit plans as an employee for a period of 12
     months, (iii) vesting of all stock options granted to you that would have
     vested by the end of the month of your termination if your employment had
     not been terminated , and (iv) bonus for the Fiscal year in which your
     employment is terminated, pro rated on a monthly basis based upon your
     termination date, if you achieved the performance criteria mutually agreed
     upon by you and the Board for the Fiscal Year. The Company shall have the
     obligation to make the payments and provide the benefits provided for in
     this section regardless of your income or effects to mitigate, if any,
     however it shall have the right to stop the payments and benefits in
     Section 5.2(i) and (ii) if at any time prior to the expiration of twelve
     months after termination, you become otherwise employed in another full
     time salaried position with benefits. In order to receive this severance
     package, you will be required to sign a release in a form acceptable to the
     Company, of any and all claims that you may have against the Company.

5.3  "Cause" means a determination in the reasonable good faith of the Board
     that you have: (a) engaged in a material act in violation of the law,
     except that if with regard to the act, you are not subsequently convicted
     of a felony or do not enter a plea of guilty or no lo contendre to a felony
     (except for ordinary traffic violations); you will be entitled to receive
     the severance package provided for in Section 5.2 (i through iv), (b)
     materially breached your fiduciary duty to the Company; (c) unreasonable
     refused to perform the good faith, lawful policies or instructions of the
     Board; or (d) failed to fully and faithfully perform your materially
     obligations under this Employment Agreement after having been given thirty
     days written notice of any such failure and an opportunity to cure. "Good
     Reason" means (i) you are assigned significant duties inconsistent with
     your position in the Company or your employment terms and responsibilities
     are materially diminished by the Company, (ii) you are required to relocate
     to a regular work location that is more than 50 miles from the Company's
     offices where you regularly work, without your approval or (iii) a material
     breach by the Company of its obligations under the Employment Agreement. If
     you wish to resign your employment for Good Reason, you will be required to
     give the Company 30 days written notice of resignation. The Company will
     have 30 days to cure the reason(s) for your resignation. If the reason(s)
     for your
<PAGE>

     resignation is/are not cured within 30 days, the period of time you have to
     exercise your stock options shall begin to run following the expiration of
     the cure period.

6.   Change in Ownership Event: For a period of twelve months following a
     "Change In Ownership Event" ("Change In Ownership Event" being defined as
     any sale of all or substantially all of the Company's assets or any merger,
     consolidation or stock sales which results in the holders of the Company's
     capital stock immediately prior to such transaction owning less than 50% of
     the voting power of the Company's capital stock immediately after such
     transaction), if (a) your employment is terminated by the Company or its
     successor for any reason other than for Cause (as defined in Section 5 of
     this Employment Agreement); or (b) you resign for Good Cause, you will be
     entitled to receive a severance package consisting of (i) vesting of any
     unvested stock options that were issued to you by the Company, (ii) 12
     months of your base salary at that time, payable in a lump sum, subject to
     normal withholding requirements, (iii) continued participation in all
     benefit plans as an employee for a period of 12 months, and (iv) bonus for
     the fiscal year in which your employment is terminated, pro rated on a
     monthly basis based upon your termination date, if you achieved the
     performance criteria mutually agreed upon by you and the Board for that
     Fiscal Year. You shall have a period of 90 days following termination of
     your employment pursuant to Section 6(a) to exercise such options. If you
     wish to resign your employment pursuant to Section 6(b), you will be
     required to give the Company 30 days written notice of resignation. The
     Company will have 30 days to cure the reason(s) for your resignation. If
     the reason(s) for your resignation is not cured within 30 days, you shall
     have a period of 90 days following the cure period to exercise such
     options. In order to receive this severance package, you will be required
     to sign a release in a form acceptable to you and the Company, of any and
     all claims that you may have against the Company.

7.   Representation and Warranty: You represent and warrant to the Company that
     the performance of your duties will not violate any agreements or trade
     secrets of any other person or entity.

8.   Standard Employee Agreements: You will be expected to sign and comply with
     the Company's standard Employment, Confidential Information and Invention
     Assignment Agreement (the "Employee NDA") which requires, among other
     provisions, the assignment of patent rights to any invention made during
     your employment at the Company and non-disclosure of proprietary
     information. Your employment will be contingent upon and not be deemed
     effective until you have executed and returned the Employee NDA to the
     Company. As provided in the Employee NDA, in the event of any dispute or
     claim relating to or arising out of our employment relationship, you and
     the Company agree that all such disputes shall be fully and finally
     resolved by binding arbitration. In addition, you will abide by the
     Company's strict policy that prohibits any employee from using or bringing
     with him or her from any pervious employer any confidential information,
     trade secrets, or proprietary materials or processes of such former
     employer. You also agree that, during the term of your employment with the
     Company, you will not actively engage in any other employment, occupation,
     consulting or other business
<PAGE>

     directly or indirectly related to the business in which the Company is now
     involved or becomes involved during the term of your employment, nor will
     you engage in any other activities that conflict with your obligations to
     the Company.

9.   Start Date: This agreement is effective as of July 21, 1999.

10.  Federal Immigration Law: For purpose of federal immigration law, you will
     be required to provide the Company documentary evidence of your identity
     and eligibility for employment in the United States. Such documentation
     must be provided to us within three (3) business days of your commencement
     date, or our employment relationship you may be terminated.

11.  Entire Agreement: This Employment Agreement, together with your Stock
     Option Agreement, and your Confidentiality and Assignment of Inventions
     Agreement, which are incorporated by reference, constitutes the entire
     agreement between the parties and supersedes all other agreements or
     understandings. This Employment Agreement can only be changed in writing,
     signed by you and the Chairman of the Board of the Company.
<PAGE>

On behalf of the Board, let me indicate how pleased I am to extend this offer,
and how much I look forward to working with you.  Please indicate your
acceptance by signing and returning the enclosed copy of this letter.

Sincerely,

TIOGA SYSTEMS, INC.


By:  /s/ Radha R. Basu
    ---------------------------------

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

The forgoing terms and conditions are hereby accepted:



Signed:  /s/ Mark Pincus
        ------------------------------


Print Name:  Mark Pincus
            --------------------------


Date: 8/1/99
      --------------------------------

      (Please note: Mr. Pincus listed no prior inventions in
                    his Employment Confidential Information
                    and Invention Assignment Agreement.)


<PAGE>

April 13, 2000

PERSONAL & CONFIDENTIAL
Mark Pincus
1572 Shrader Street
San Francisco, CA  94117

Dear Mark:

This letter is to confirm the agreement between you and Support.com, Inc. (the
"Company") regarding the mutually agreed upon decision to amend your employment
agreement with Support.com dated August 1, 1999 ("Employment Agreement").  The
amended terms of your employment relationship with the company are as set forth
below.  Except as expressly stated herein, the terms of this amendment supersede
and replace the terms of your Employment Agreement.

1. Position:  You will be the Chairman and Founder of the Company, reporting to
   the Board of Directors. As such, you will have such responsibilities as
   determined by the Board of Directors.

2. Base Salary: You will be paid a base salary of $15,000 per month.  Your
   salary will be payable in accordance with the Company's standard payroll
   policies (subject to normal required withholding). You will receive a
   vacation and benefit package similar to that provided for all other executive
   level employees.

3. Part-Time At-Will Employment: You will be an employee-at-will, meaning that
   either you or the Company can terminate your employment relationship at any
   time, for any reason, with or without Cause, and with or without notice.  You
   agree to devote more than 50% of your business time and attention to the
   Company.

4. Time and Attention Less Than 50%: At anytime during the term of your
   employment, you may give written notice to the Company stating that you
   intend to devote less than 50% of your time and attention to the Company. At
   such time you will no longer be entitled to any base salary pursuant to
   Section 2 above.

5. Stock: You will be entitled to vest according to the vesting schedules of
   your outstanding option awards (as set forth in the Employment Agreement),
   but in consideration for the reduction in your time and attention to the
   Company, such vesting shall continue only through December 31, 2000. Such
   vesting to occur regardless of employment status with the Company. Any
   remaining option shares that would have vested after December 31, 2000 will
   be considered cancelled by this
<PAGE>

     amendment to the Employment Agreement and you agree to execute any
     amendments to the applicable Option Agreements, accordingly. With respect
     to any shares of the Company in which you have an interest, you agree to
     comply with all Federal and state securities laws related to reporting and
     other compliance requirements, including Sections 13 and 16 of the
     Securities Exchange Act of 1934.

6.   Termination of Employment:

6.1  In the event your employment is terminated by the Company with or without
     Cause, as defined herein, or you resign with or without Good Reason, as
     defined herein, you will be entitled to payment of (i) accrued salary,
     benefits and reimbursable expenses owing to you through the date of such
     termination, and (ii) if applicable, any bonus you earned for the Fiscal
     Year preceding the date of your termination if it has not been paid as of
     the date of your termination.

6.2  If your employment is terminated by the Company, for any reason other than
     for Cause, or is terminated by you for Good Reason, in addition to the
     payments provided for in Section 6.1, you will be entitled to receive a
     severance package consisting of (i) your base monthly salary, paid as
     though you were still employed by the Company for a period of 12 months in
     installments, subject to appropriate deductions, (ii) continued
     participation in all benefit plans as an employee for a period of 12
     months, subject to Section 5 above, (iii) if applicable, any bonus for the
     Fiscal year in which your employment is terminated, pro rated on a monthly
     basis based upon your termination date, if you achieved performance
     criteria mutually agreed upon by you and the Board for the Fiscal Year. The
     Company shall have the obligation to make the payments and provide the
     benefits provided for in this section regardless of your income or effects
     to mitigate, if any, however it shall have the right to stop the payments
     and benefits in Section 6.2(i) and (ii) if at any time prior to the
     expiration of twelve (12) months after termination, you become otherwise
     employed in another position in which you are dedicating more than fifty
     percent (50%) of your business time and attention. In order to receive this
     severance package, you will be required to sign a release in a form
     acceptable to the Company, of any and all claims that you may have against
     the Company.

6.3  "Cause" and "Good Reason" shall have the meaning set forth in your
     Employment Agreement. If you wish to resign your employment for Good
     Reason, you will be required to give the Company thirty (30) days written
     notice of resignation. The Company will have thirty (30) days to cure the
     reason(s) for your resignation. If the reason(s) for your resignation
     is/are not cured within thirty (30) days, the period of time you have to
     exercise your stock options shall begin to run following the expiration of
     the cure period.

7.   Change in Ownership Event: For a period of twelve (12) months following a
     "Change In Ownership Event" ("Change In Ownership Event" being defined as
     any sale of all or substantially all of the Company's assets or any merger,
     consolidation or stock sales which results in the holders of the Company's
     capital stock immediately prior to such transaction owning less than fifty
     percent (50%) of the voting power of
<PAGE>

     the Company's capital stock immediately after such transaction), if (a)
     your employment is terminated by the Company or its successor for any
     reason other than for Cause (as defined in Section 5 of your Employment
     Agreement); or (b) you resign for Good Cause (as defined in Section 5 of
     your Employment Agreement), you will be entitled to receive a severance
     package consisting of (i) vesting of any unvested stock options that were
     issued to you by the Company, subject to Section 5 above, (ii) twelve (12)
     months of your base salary at that time, payable in a lump sum, subject to
     normal withholding requirements, (iii) continued participation in all
     benefit plans as an employee for a period of twelve (12) months, subject to
     Section 5 above, and (iv) if applicable, any bonus for the Fiscal Year in
     which your employment is terminated, pro rated on a monthly basis based
     upon your termination date, if you achieved performance criteria mutually
     agreed upon by you and the Board for that Fiscal Year. You shall have a
     period of ninety (90) days following termination of your employment
     pursuant to Section 7(a) to exercise such options. If you wish to resign
     your employment pursuant to Section 7(b), you will be required to give the
     Company thirty (30) days written notice of resignation. The Company will
     have thirty (30) days to cure the reason(s) for your resignation. If the
     reason(s) for your resignation is not cured within thirty (30) days, you
     shall have a period of ninety (90) days following the cure period to
     exercise such options. In order to receive this severance package, you will
     be required to sign a release in a form acceptable to you and the Company,
     of any and all claims that you may have against the Company.

8.   Representation and Warranty: You represent and warrant to the Company that
     the performance of your duties will not violate any agreements or trade
     secrets of any other person or entity.

9.   Standard Employee Agreements: You will be expected to continue to comply
     with the Company's standard Employment, Confidential Information and
     Invention Assignment Agreement you signed on __________ (the "Employee
     NDA") which requires, among other provisions, the assignment of patent
     rights to any invention made during your employment at the Company and non-
     disclosure of proprietary information. Your employment will be contingent
     upon your compliance with the Employee NDA. As provided in the Employee
     NDA, in the event of any dispute or claim relating to or arising out of our
     employment relationship, you and the Company agree that all such disputes
     shall be fully and finally resolved by binding arbitration. In addition,
     you will abide by the Company's strict policy that prohibits any employee
     from using or bringing with him or her from any pervious employer any
     confidential information, trade secrets, or proprietary materials or
     processes of such former employer. You also agree that, during the term of
     your employment with the Company, you will not actively engage in any other
     employment, occupation, consulting or other business directly or indirectly
     related to the business in which the Company is now involved or becomes
     involved during the term of your employment, nor will you engage in any
     other activities that conflict with your obligations to the Company.

10.  Start Date: This amendment to your Employment Agreement is effective as of
     April __, 2000.
<PAGE>

11.  Entire Agreement: This amendment, your Employment Agreement, and your
     Confidentiality and Assignment of Inventions Agreement, which are
     incorporated by reference, constitute the entire agreement between the
     parties and supersedes all other agreements or understandings. This
     Employment Agreement can only be changed in writing, signed by you and the
     CEO of the Company.

On behalf of the Board, let me indicate how pleased I am to extend this offer,
and how much I look forward to continue working with you.  Please indicate your
acceptance to the terms of the amendment to your Employment Agreement by signing
and returning the enclosed copy of this letter.

Sincerely,

SUPPORT.COM, INC.


By:  /s/ Radha R. Basu
    ---------------------------------

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

The forgoing terms and conditions are hereby accepted:



Signed:  /s/ Mark Pincus
       ------------------------------


Print Name:  Mark Pincus
           --------------------------


Date:  4/21/00
     --------------------------------