<PAGE>   1
Exhibit number 4.4b



                                    AMENDMENT NO. 1, dated as of February 25,
                           2000 (this "Amendment"), in respect of the Credit
                           Agreement dated as of July 16, 1999 (the "Credit
                           Agreement" and, as amended by this Amendment, the
                           "Amended Credit Agreement"), among Gartner Group,
                           Inc. (the "Borrower"), the Lenders party thereto,
                           and The Chase Manhattan Bank, as Administrative
                           Agent (in such capacity, the "Administrative
                           Agent").

                  The Borrower has requested that the Credit Agreement be
amended as set forth below, and the parties hereto are willing so to amend the
Credit Agreement. Each capitalized term used but not defined herein has the
meaning assigned thereto in the Credit Agreement.

                  In consideration of the premises and the agreements,
provisions and covenants herein contained, the parties hereto hereby agree, on
the terms and subject to the conditions set forth herein, as follows:

                  SECTION 1.  Amendments.  Upon the effectiveness of this
Amendment as provided in Section 3 below, the Credit Agreement shall be amended
as follows:

                  (a) Section 1.01 of the Credit Agreement is hereby amended by
inserting the following defined terms in their alphabetical positions:

                  "Permitted Capital Obligations" means Permitted Preferred
         Stock or Permitted Subordinated Debt.

                  "Permitted Capital Obligations Effective Date" means the
         first date on which the Borrower has issued Permitted Capital
         Obligations for gross cash proceeds to the Borrower of at least
         $175,000,000.

                  "Permitted Preferred Stock" means preferred stock issued by
         the Borrower that (a) does not require any repurchase or redemption
         (other than conversion or exchange into Common Stock), whether
         contingent or not, prior to the date that is eight months after the
         Term Maturity Date and (b) is on terms and conditions that are
         reasonably acceptable to the Administrative Agent, and otherwise is on
         terms customary in the relevant





<PAGE>   2

         capital markets for preferred stock issued by issuers similar to the
         Borrower.

                  "Permitted Subordinated Debt" means subordinated, unsecured
         Indebtedness of the Borrower that (a) requires no scheduled cash
         payments of principal and no mandatory repurchase or redemption
         obligations prior to the date that is eight months after the Term
         Maturity Date, (b) does not impose any financial or other
         "maintenance" covenants on the Borrower or any of the Subsidiaries,
         (c) is not guaranteed by any Subsidiaries and (d) contains customary
         subordination terms that are reasonably acceptable to the
         Administrative Agent, and otherwise is on terms and conditions
         customary in the relevant capital markets for subordinated
         indebtedness issued by issuers similar to the Borrower.

                  "Specified Asset Sales" means the sales by the Borrower of
         all or any substantial part of its equity interests in Jupiter
         Communications, Inc. or NetG, Inc.

                  "Total Senior Balance Sheet Indebtedness" means, at any date,
         Total Balance Sheet Indebtedness on such date minus the amount of
         outstanding Permitted Subordinated Debt that would be reflected on a
         consolidated balance sheet of the Borrower prepared in accordance with
         GAAP as of such date.

                  "Wildcats Acquisition" means the acquisition by the Borrower
         of at least 75% of the capital stock of the entity known as "Wildcats"
         (the identity of which has been notified to the Administrative Agent
         and the Lenders), which acquisition is made for consideration that is
         funded entirely from a Term Borrowing made after February 15, 2000.

                  (b)   The definition of "Applicable Rate" in Section 1.01 of
the Credit Agreement is hereby amended by (i) replacing "Category 2" with
"Category 5" prior to the table therein and (ii) deleting the table therein and
replacing it with the following:

<TABLE>
<CAPTION>
===========================================================================================================
                                             ABR              Eurodollar             Commitment Fee
                                             ---              ----------             --------------
           Leverage Ratio:                  Spread              Spread                    Rate
           ---------------                  ------              ------                    ----
-----------------------------------------------------------------------------------------------------------
<S>                                        <C>                <C>                     <C>
              Category 1
              ----------                    1.25%               2.50%                     0.50%
       GREATER THAN OR EQUAL TO 3.25x
-----------------------------------------------------------------------------------------------------------
              Category 2
              ----------
       GREATER THAN OR EQUAL TO 3.00x but   1.00%               2.25%                     0.50%
       LESS THAN    3.25x
-----------------------------------------------------------------------------------------------------------
              Category 3                    0.75%               2.00%                     0.50%
              ----------
</TABLE>



<PAGE>   3

<TABLE>
<CAPTION>
===========================================================================================================
                                             ABR              Eurodollar             Commitment Fee
                                             ---              ----------             --------------
           Leverage Ratio:                  Spread              Spread                    Rate
           ---------------                  ------              ------                    ----
-----------------------------------------------------------------------------------------------------------
<S>                                          <C>                  <C>                     <C>
       GREATER THAN EQUAL TO 2.75x but
       LESS THAN    3.00x
-----------------------------------------------------------------------------------------------------------
              Category 4
              ----------
       GREATER THAN OR EQUAL TO 2.25x but      0.50%               1.75%                     0.35%
       LESS THAN    2.75x
-----------------------------------------------------------------------------------------------------------

              Category 5
              ----------
       GREATER THAN OR EQUAL TO 1.75x but      0.25%               1.50%                     0.30%
       LESS THAN    2.25x
-----------------------------------------------------------------------------------------------------------
              Category 6
              ----------
       GREATER THAN OR EQUAL TO 1.25x but        0%                1.25%                     0.30%
       LESS THAN    1.75x
-----------------------------------------------------------------------------------------------------------
              Category 7
              ----------
       GREATER THAN OR EQUAL TO 1.00x but        0%                1.00%                     0.30%
       LESS THAN    1.25x
-----------------------------------------------------------------------------------------------------------
              Category 8
              ----------                         0%                0.75%                     0.25%
       LESS THAN    1.00x
===========================================================================================================
</TABLE>


                  (c)   The definition of "Consolidated Cash Interest Expense"
in Section 1.01 of the Credit Agreement is hereby amended by replacing "plus
(iii)" in clause (a) therein with ", (iii) cash payments made during such
period to holders of Permitted Preferred Stock, plus (iv)".

                  (d)   The definition of "Permitted Acquisitions" in Section
1.01 of the Credit Agreement is hereby amended by (i) inserting "(i)" after the
word "means" therein, (ii) inserting after "2.25 to 1.00" the words "(or 2.75
to 1.00, in the case of acquisitions made after the Permitted Capital
Obligations Effective Date)" and (iii) adding immediately before the period at
the end thereof the words "and (ii) the Wildcats Acquisition".

                  (e)   The definition of "Prepayment Event" in Section 1.01 of
the Credit Agreement is hereby amended by (i) inserting "(i)" after the word
"means" therein and (ii) adding immediately before the period at the end
thereof the words "or (ii) the completion of any of the Specified Asset Sales".

                  (f)   Section 2.09(c) of the Credit Agreement is hereby
amended by (i) inserting after "2.25 to 1.00" the words "(or 2.75 to 1.00, in
the case of Prepayment





<PAGE>   4


Events occurring after the Permitted Capital Obligations Effective Date)" and
(ii) adding the following proviso before the period at the end thereof: ";
provided, that 100% of the Net Proceeds received in respect of the Specified
Asset Sales and the issuance of Permitted Capital Obligations shall be used to
prepay Term Loans to the extent and only to the extent that the aggregate
amount of Term Loans prepaid pursuant to this proviso does not exceed
$200,000,000".

                  (g)   Section 5.01(c) of the Credit Agreement is hereby
amended by replacing "6.14 and 6.15" therein with "6.14, 6.15 and 6.17".

                  (h)   Section 6.03 of the Credit Agreement is hereby amended
by replacing "6.14 and 6.15" therein with "6.14, 6.15 and 6.17".

                  (i)   Section 6.05 of the Credit Agreement is hereby amended
by (i) deleting "and" at the end of clause (c) thereof, (ii) replacing the
period at the end of clause (d) thereof with "; and" and (iii) adding the
following new clause (e) at the end thereof:

                  (e)   Specified Asset Sales.

                  (j)   Section 6.08 of the Credit Agreement is hereby amended
by (i) inserting the words "the Borrower may make" at the beginning of clauses
(viii) and (ix) therein, (ii) deleting the "and" at the end of clause (viii)
therein and (iii) inserting before the period at the end thereof "; and (x) the
Borrower may pay cash dividends to holders of Permitted Preferred Stock,
provided, that, after giving effect to any such dividend on a pro forma basis
as if such dividend had been made on the last day of the fiscal quarter most
recently ended on or prior to the date of such dividend, the Borrower would be
in compliance with Sections 6.12, 6.13 and 6.17".

                  (k)   Section 6.12 of the Credit Agreement is hereby amended
by replacing "5.00 to 1.00" with "(i) 3.50 to 1.00, for the periods of four
consecutive fiscal quarters ending March 31, 2000, June 30, 2000 and September
30, 2000, respectively, and (ii) 4.50 to 1.00, for all other periods".

                  (l)   Section 6.13 of the Credit Agreement is hereby amended
by replacing "2.75 to 1.00" with "(a) prior to the Permitted Capital
Obligations Effective Date,


<PAGE>   5


(i) 3.50 to 1.00 for the fiscal quarter ending March 31, 2000, (ii) 3.25 to 1.00
for the fiscal quarter ending June 30, 2000 and (iii) 2.75 to 1.00 for all other
fiscal quarters and (b) on or after the Permitted Capital Obligations Effective
Date, 3.50 to 1.00, for all fiscal quarters".

                  (m)   The following new Sections 6.17 and 6.18 are hereby
added to the Credit Agreement following Section 6.16 thereof:

                  SECTION 6.17. Total Senior Balance Sheet Indebtedness to
         EBITDA. On or after the Permitted Capital Obligations Effective Date,
         the Borrower will not permit the ratio of (a) Total Senior Balance
         Sheet Indebtedness as of the last day of any fiscal quarter to (b)
         Consolidated EBITDA for the period of four consecutive fiscal quarters
         ending with such fiscal quarter, to exceed 2.00 to 1.00.

                  SECTION 6.18. Other Indebtedness and Agreements. The Borrower
         will not, nor will it permit any Subsidiary to, make any distribution,
         whether in cash, property, securities or a combination thereof, other
         than regular scheduled payments as and when due, in respect of, or
         pay, or offer or commit to pay, or directly or indirectly redeem,
         repurchase, retire or otherwise acquire for consideration, or set
         apart any sum for the aforesaid purposes, any Permitted Subordinated
         Debt, in each case except for any conversion of Permitted Subordinated
         Debt into Common Stock or Permitted Preferred Stock.

                  SECTION 2.  Representations and Warranties.  The Borrower
represents and warrants as of the date hereof to each of the Lenders that:

                  (a) Before and after giving effect to this Amendment, the
representations and warranties set forth in the Credit Agreement and the other
Loan Documents are true and correct in all material respects with the same
effect as if made on the date hereof, except to the extent such representations
and warranties expressly relate to an earlier date.



<PAGE>   6


                  (b) Immediately before and after giving effect to this
Amendment, no Event of Default or Default has occurred and is continuing.

                  SECTION 3.  Conditions to Effectiveness.  The amendments set
forth in Section 1 of this Amendment shall become effective, as of the date
hereof, on the date (the "Amendment Closing Date") on which the Administrative
Agent shall have received (a) counterparts of this Amendment that, when taken
together, bear the signatures of the Borrower, the Administrative Agent, the
Subsidiary Loan Parties and the Required Lenders, (b) an amendment fee, for
distribution to each Lender that has returned a signed counterpart of this
Amendment to the Administrative Agent or its counsel by 12:00 p.m. New York
City time on February 25, 2000, equal to a percentage notified to the Lenders
by the Borrower of the aggregate Commitments of each such signing Lender, (c)
payment of all fees and expenses (to the extent invoiced prior to the Amendment
Closing Date) payable to The Chase Manhattan Bank and Chase Securities Inc. in
connection with this Amendment and (d) a legal opinion of in-house counsel to
the Borrower and such certificates relating to the authorization and execution
of this Amendment as the Administrative Agent may reasonably request, in each
case in form and substance reasonably satisfactory to the Administrative Agent.
The provisions of Section 1 shall terminate and cease to be of any force or
effect if the Amendment Closing Date shall not have occurred on or prior to
February 29, 2000 (or such later date, prior to March 4, 2000, as the
Administrative Agent and the Borrower may agree).

                  SECTION 4.  Agreement.  Except as specifically stated herein,
the provisions of the Credit Agreement are and shall remain in full force and
effect. As used therein, the terms "Credit Agreement", "herein", "hereunder",
"hereinafter", "hereto", "hereof" and words of similar import shall, unless the
context otherwise requires, refer to the Amended Credit Agreement.

                  SECTION 5.  APPLICABLE LAW.  THIS AMENDMENT SHALL BE GOVERNED
BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

                  SECTION 6.  Counterparts.  This Amendment may be executed in
two or more counterparts, each of which



<PAGE>   7


shall constitute an original but all of which when taken together shall
constitute but one contract.

                  SECTION 7.  Expenses.  The Borrower agrees to reimburse the
Administrative Agent for all reasonable out-of-pocket expenses incurred by it
in connection with this Amendment, including the reasonable fees, charges and
disbursements of Cravath, Swaine & Moore, counsel for the Administrative Agent.


<PAGE>   8



                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be duly executed by their respective  authorized officers as of
the day and year first written above.



                                             GARTNER GROUP, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             COMPUTER AND COMMUNICATION
                                             INFORMATION GROUP, INC.,

                                               by
                                                      ------------------------
                                                      Name:
                                                      Title:


                                             CPULSE LLC,

                                               by
                                                      ------------------------
                                                      Name:
                                                      Title:


                                             DATAQUEST INCORPORATED,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             DATAQUEST (KOREA) INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:



<PAGE>   9


                                             DECISION DRIVERS, INC,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             GARTNER FUND I, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             GARTNER FUND II, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             GARTNER ENTERPRISES LTD.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             GARTNER GROUP LEARNING, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             G.G. GLOBAL HOLDINGS, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:



<PAGE>   10


                                             G.G. INVESTMENT MANAGEMENT, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:



                                             G.G. CREDIT INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             G.G. WEST CORPORATION,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             GRIGGS-ANDERSON, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             THE RESEARCH BOARD, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             THE WARNER GROUP,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:



<PAGE>   11

                                             VISION EVENTS INTERNATIONAL, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             VUE ACQUISITION CORPORATION,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:



                                             G.G. CANADA, INC.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             INTECO CORPORATION,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             THE CHASE MANHATTAN BANK,
                                             individually and as
                                             Administrative Agent,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:




<PAGE>   12


                                             CREDIT SUISSE FIRST BOSTON,
                                             individually and as
                                             Syndication Agent,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             FLEET NATIONAL BANK,
                                             individually and as
                                             Documentation Agent,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:

                                             BANCO ESPIRITO SANTO E
                                             COMERCIAL DE LISBOA, NASSAU
                                             BRANCH,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             BANK LEUMI USA,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:



<PAGE>   13

                                             THE BANK OF NEW YORK,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:

                                             THE BANK OF NOVA SCOTIA,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             BANK OF AMERICA, N.A.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             BANKBOSTON, N.A.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             COMERICA BANK,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             DAI ICHI KANGYO BANK, LTD.,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:




<PAGE>   14


                                             DEUTSCHE BANK A.G., NEW YORK
                                             AND/OR CAYMAN ISLANDS
                                             BRANCHES,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             THE FIRST CHICAGO NATIONAL BANK,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             FIRST UNION NATIONAL BANK,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             THE FUJI BANK, LIMITED,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             IBM CREDIT CORPORATION,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:




<PAGE>   15


                                             MERCANTILE BANK, NATIONAL
                                             ASSOCIATION,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             NATIONAL CITY BANK,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             PEOPLE'S BANK,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             CITIZENS BANK OF
                                             MASSACHUSETTS,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             THE SUMITOMO BANK, LIMITED,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title:


                                             SUNTRUST BANK,

                                               by
                                                      -------------------------
                                                      Name:
                                                      Title: