<PAGE>

                                                                    Exhibit 10.6

                              VSTREAM INCORPORATED

                                 FIRST AMENDMENT
                                       TO
                    AMENDED AND RESTATED INVESTORS AGREEMENT

     This First Amendment to the Amended and Restated Investors Agreement dated
as of November 17, 1999 (the "Investors Agreement"), is entered into as of
December 15, 1999, by and among VStream Incorporated, a Delaware corporation
(the "Company"), and the parties identified as additional investors on the
signature pages attached hereto (the "Additional Investors") (this "First
Amendment").

                                    RECITALS

     Whereas, the Company and the holders of the Company's Series B Preferred
Stock, Series C Preferred Stock, Series D Preferred Stock identified on the
signature pages thereto, are parties to the Investors Agreement;

     Whereas, in connection with and as a condition to the purchase by the
Additional Investors of 4,761,334 shares of the Company's Series D Preferred
Stock, the Company has agreed to provide the Additional Investors the rights set
forth in the Investors Agreement;

     Whereas, under Section 3.1 of the Investors Agreement, the Investors
Agreement may be amended with written consent of the Company and the holders of
at least 66-2/3% of the outstanding shares of Investor Stock (as defined in the
Investors Agreement );and

     Whereas, at least 66-2/3% of the shares of Investor Stock have consented in
writing to this First Amendment.

     In consideration of the mutual agreements, covenants and considerations
contained herein, the parties hereto agree as follows:

     1.   Amendment. The first paragraph of the Investors Agreement is hereby
amended in its entirety to read as follows:

          This Investors Agreement (this "Agreement") dated as of November 17,
          1999, is entered into by and among (i) VStream Incorporated, a
          Delaware corporation (the "Company"), (ii) the holders of the
          Company's Series B Preferred Stock, Series C Preferred Stock and
          Series D Preferred Stock identified on the signature pages hereto (the
          "Initial Investors"), and (iii) the parties identified as additional
          investors on the signature pages hereto (the "Additional Investors").
          The Initial Investors and the Additional Investors are collectively
          referred to herein as the "Investors."

                                       1
<PAGE>

     2. Definitions. All capitalized terms used herein without definition shall
have the meanings ascribed to them in the Investors Agreement.

     3. Additional Investors. Upon the effectiveness of this First Amendment,
the Additional Investors agree to be bound by all of the terms and conditions of
the Investors Agreement as amended herein.

     4. Notices. All notices sent to the Company pursuant to the Stockholders'
Agreement shall be sent to the Company at 1157 Century Drive, Louisville.
Colorado 80027.

     5. Effect of Amendment. Except as amended as set forth above, the Investors
Agreement shall continue in full force and effect.

     6. Governing Law. This First Amendment shall be governed and construed in
accordance with the laws of the State of Colorado as though made solely among
residents of the State of Colorado without regard to conflicts of law
principals.

            [The Remainder of this Page is Intentionally Left Blank.]

                                       2
<PAGE>

     IN WITNESS WHEREOF, the undersigned parties have executed this First
Amendment to the Amended and Restated Investors Agreement as of the date set
forth in the first paragraph hereof.

                                       COMPANY:

                                       VSTREAM INCORPORATED


                                       By: /s/ Paul A. Berberian
                                           ---------------------------------
                                       Title: CEO
                                              ------------------------------

                                 [Signature Page to First Amendment to Investors
                                 Agreement]

                                       3
<PAGE>

                                  ADDITIONAL INVESTORS:

                                  CENTENNIAL FUND VI, L.P.

                                  By: Centennial Holdings VI, LLC
                                      Its General Partner

                                  By: /s/ Donald H. Parsons, Jr.
                                     ------------------------------------------
                                     Donald H. Parsons, Jr., Managing Principal

                                  CENTENNIAL ENTREPRENEURS FUND VI, L.P.

                                  By: Centennial Holdings VI, LLC
                                      Its General Partner

                                  By: /s/ Donald H. Parsons, Jr.
                                     ------------------------------------------
                                     Managing Principal

                                  CENTENNIAL HOLDINGS I, LLC

                                  By: /s/ Donald H. Parsons, Jr.
                                     ------------------------------------------
                                     Donald H. Parsons, Jr., Sr. Vice President

                                  UNIVERSITY OF COLORADO FOUNDATION, INC.

                                  By: /s/
                                     ------------------------------------------

                                  Title:
                                        ---------------------------------------


                                  [Signature Page to First Amendment to
                                  Investors Agreement]

                                       4


<PAGE>

                          /s/ Kim N.C. Tomsic
                          ------------------------------------------------------
                          Kim N.C. Tomsic

                          /s/ John L. Kurtz, Jr.
                          ------------------------------------------------------
                          John L. Kurtz, Jr.

                          /s/ Lori K. Bornheimer
                          ------------------------------------------------------
                          Lori K. Bornheimer

                          /s/ Frances L. Berberian
                          ------------------------------------------------------
                          Frances L. Berberian

                          /s/ Charles O. Higgins
                          ------------------------------------------------------
                          Charles O. Higgins

                          /s/ Byron R. Chrisman
                          ------------------------------------------------------
                          Byron R. Chrisman

                          /s/ T. Charles Fial
                          ------------------------------------------------------
                          T. Charles Fial TTEE FBO T. Charles Fial 1997
                          Revocable trust DTD 9/30/97

                          /s/ Eva Garibian
                          ------------------------------------------------------
                          Eva Garibian

                          /s/ Vahe Garibian
                          ------------------------------------------------------
                          Vahe Garibian

                          /s/ Mathew S. Martin
                          ------------------------------------------------------
                          Mathew S. Martin

                          /s/ Karen S. Martin
                          ------------------------------------------------------
                          Karen S. Martin

                          /s/ Thomas Patsiga
                          ------------------------------------------------------
                          Thomas Patsiga

                          /s/
                          ------------------------------------------------------
                          Charles Schwab & Co., Inc. FBO Austin R. Gibbons
                          IRA Acct #36500127

                          /s/ Jarvis Seccombe
                          ------------------------------------------------------
                          Jarvis Seccombe


                          [Signature Page to First Amendment to
                          Stockholders' Agreement]

                                       5

<PAGE>

                                  /s/ Diane Seccombe
                                  -------------------------------------
                                  Diane Seccombe

                                  /s/ Rimvydas Ambraziunas
                                  -------------------------------------
                                  Rimvydas Ambraziunas

                                  /s/ Marsha Ambraziunas
                                  -------------------------------------
                                  Marsha Ambraziunas

                                  /s/ Francis X. Malone
                                  -------------------------------------
                                  Francis X. Malone

                                  /s/ David A. Makarechian
                                  -------------------------------------
                                  David A. Makarechian

                                  /s/ Jeremy W. Makarechian
                                  -------------------------------------
                                  Jeremy W. Makarechian

                                  /s/ Alfred E. Moore
                                  -------------------------------------
                                  Alfred E. Moore

                                  /s/ Joanne L. Moore
                                  -------------------------------------
                                  Joanne L. Moore

                                  /s/ Philippe Muller
                                  -------------------------------------
                                  Philippe Muller


                                  [Signature Page to First Amendment to
                                  Investors Agreement]

                                       6

<PAGE>

                                SOFTBANK TECHNOLOGY VENTURES V, L.P.

                                By:    STV IV LLC

                                By: /s/ Bradley A. Feld
                                   -------------------------------
                                Managing Director


                                SOFTBANK TECHNOLOGY VENTURES ADVISORS
                                FUND V, L.P.

                                By:    STV IV LLC

                                By: /s/ Bradley A. Feld
                                   -------------------------------
                                Managing Director


                                SOFTBANK TECHNOLOGY VENTURES
                                ENTREPRENEURS FUND V, L.P.

                                By:    STV IV LLC

                                By: /s/ Bradley A. Feld
                                   -------------------------------
                                Managing Director


                                SOFTBANK TECHNOLOGY VENTURES IV, L.P.

                                By:    STV IV LLC

                                By: /s/ Bradley A. Feld
                                   -------------------------------
                                Managing Director


                                SOFTBANK TECHNOLOGY ADVISORS FUND, L.P.

                                By:    STV IV LLC

                                By: /s/ Bradley A. Feld
                                   -------------------------------
                                Managing Director


                                [Signature Page to First Amendment to Investors
                                Agreement]

                                       7