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                                                                     EXHIBIT 5.1

                                  July 21, 2000

Network Associates, Inc.
3965 Freedom Circle
Santa Clara, California 95054

        RE: REGISTRATION STATEMENT ON FORM S-8

Ladies and Gentlemen:

        We have examined the Registration Statement on Form S-8 to be filed by
you with the Securities and Exchange Commission on or about July 21, 2000 , in
connection with the registration under the Securities Act of 1933, as amended,
of 3,000,000 shares of Common Stock to be issued under the Company's 2000
Nonstatutory Stock Option Plan and 6,000,000 shares of Common Stock to be issued
under the Company's 1997 Stock Incentive Plan, as amended. Such shares are,
collectively, referred to herein as the "Shares" and the 2000 Nonstatutory Stock
Option Plan and the 1997 Stock Incentive Plan, as amended, are referred to
herein as the "Plans."

        As your legal counsel, we have examined the proceedings taken and are
familiar with the proceedings proposed to be taken by you in connection with the
sale and issuance of the Shares under the Plans.

        It is our opinion that the Shares, when issued and sold in the manner
referred to in the Plans, and pursuant to the agreements which accompany the
Plans, will be legally and validly issued, fully paid and nonassessable.

        We consent to the use of this opinion as an exhibit to said Registration
Statement and further consent to the use of our name wherever appearing in said
Registration Statement and any amendments thereto.

                                            Sincerely,

                                            WILSON SONSINI GOODRICH & ROSATI
                                            Professional Corporation

                                            /s/ WILSON SONSINI GOODRICH & ROSATI