Agreement and Plan of Contribution, Investment and Merger - National Broadcasting Co. Inc., NBC Internet Inc. and Xoom.com Inc.

                                                               EXECUTION COPY
                                          
                                          
                                          
         FIRST AMENDMENT TO SECOND AMENDED AND RESTATED AGREEMENT AND PLAN
                       OF CONTRIBUTION, INVESTMENT AND MERGER
                                          
     This First Amendment to Second Amended and Restated Agreement and Plan of
Contribution, Investment and Merger, dated as of October 20, 1999 (hereinafter,
'Amendment No. 1'), among National Broadcasting Company, Inc., a Delaware
corporation ('NBC'), GE Investments Subsidiary, Inc., a Delaware corporation,
Neon Media Corporation, a Delaware Corporation, NBC Internet, Inc., a Delaware
corporation ('NBCi,' referred to as 'Xenon 2' in the Original Contribution
Agreement hereinafter identified), and XOOM.com, Inc.,  a Delaware corporation 
('Xoom')
                                          
                                W I T N E S S E T H:

     WHEREAS, the parties hereto have previously entered into that certain
Second Amended and Restated Agreement and Plan of Contribution, Investment and
Merger dated as of July 8, 1999 (the 'Original Contribution Agreement'); and

     WHEREAS, the parties now wish to amend the Original Contribution Agreement
as provided below;

     NOW THEREFORE, the Original Contribution Agreement is amended in the
following respects:

     1.   Section 5.2(b) of the Original Contribution Agreement is amended in
its entirety to provide as follows:

          '(b) issue, purchase or redeem, or authorize or propose the issuance,
     purchase or redemption of, or make any distribution with respect to, any
     equity interests of SNAP or any class of securities convertible into, or
     rights, warrants or options to acquire, any such equity interests or other
     convertible securities, other than (i) pursuant to employee options
     outstanding on the date hereof or issued in accordance herewith, (ii) SNAP
     Options issued pursuant to commitments to issue SNAP Options that were
     included in job offers outstanding as of May 9, 1999, as identified on
     SCHEDULE 4.1(t) as amended and (iii) additional options that, when added to
     SNAP Options previously outstanding, do not exceed options for units equal
     in number to 17% of the units of SNAP.'

     2.   SCHEDULE 3.7 to the Original Contribution Agreement is amended by
replacing the reference to 'Thomas Rogers' under the item 'NBC Directors' with a
reference to 'Scott M. Sassa'.

     3.   SCHEDULE 4.2(t) to the Original Contribution Agreement is amended by
the addition thereto of the items listed on SCHEDULE 4.2(t)-2 hereto.



     4.   SCHEDULE 6.9 to the Original Contribution Agreement is amended by
deleting the reference to 'August 25, 1998' and replacing it with 'September 14,
1999,' and the parties acknowledge and agree that NBCi shall, accordingly, be
obligated pursuant to Section 6.9 of the Contribution Agreement to repay and
terminate the indebtedness represented by that certain Credit Agreement dated
September 14, 1999 between SNAP and Bank of America National Trust and Savings
Association, and use its best efforts to cause the guarantee of such
indebtedness by General Electric Company to be fully released immediately
following the Closing.

     5.   EXHIBIT A to the Original Contribution Agreement is amended by
increasing the value of the Spots to be provided by NBC to Xenon 2 to $405
million and by establishing that the aggregate value of the Spots to be provided
in the fourth quarter of 1999 shall be no less than $45 million.

     6.   In all other respects, the Original Contribution Agreement is
unchanged and shall remain in full force and effect.

     7.   GOVERNING LAW.  THIS AMENDMENT NO. 1 SHALL BE GOVERNED AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK APPLICABLE TO AGREEMENTS
MADE TO BE PERFORMED WITHIN SUCH STATE.
     

     [THE REMAINDER OF THIS PAGE IS INTENTIONALLY BLANK.]



8.     Article X of the Original Merger Agreement shall apply MUTATIS MUTANDIS
to this Amendment No. 1.

     IN WITNESS WHEREOF, the parties have caused this Amendment No. 1 to be duly
executed as of the date first above written.

                         NATIONAL BROADCASTING COMPANY, INC.

                         BY: /s/ Martin Yudkovitz
                             --------------------
                         
                         Name: Martin Yudkovitz
                         Title: President, NBC Interactive
                         
                         GE INVESTMENTS SUBSIDIARY, INC.

                         BY: /s/ Robert E. Healing
                             ---------------------
                         
                         Name: Robert E. Healing
                         Title: Vice President
                         
                         NEON MEDIA CORPORATION

                         BY: /s/ Martin Yudkovitz
                             --------------------
                         Name: Martin Yudkovitz
                         Title: President, NBC Interactive
                         
                         NBC INTERNET, INC. (formerly, Xenon 2, Inc.)

                         BY: /s/ John Harbottle
                             ------------------

                         Name: John Harbottle
                         Title: Chief Financial Officer and 
                                Executive Vice President
                         
                         XOOM.COM, INC.

                         BY: /s/ John Harbottle
                             ------------------
                         Name: John Harbottle
                         Title: Chief Financial Officer and 
                                Executive Vice President