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                                                                     EXHIBIT 5.1

                [Letterhead of Wilson Sonsini Goodrich & Rosati]

                               February 25, 2002

Hewlett-Packard Company
3000 Hanover Street
Palo Alto, California 94304

    RE: HEWLETT-PACKARD COMPANY--REGISTRATION STATEMENT ON FORM S-3

Ladies and Gentlemen:

    At your request, we have examined the Registration Statement on Form S-3
(the "Registration Statement"), to be filed by Hewlett-Packard Company, a
Delaware corporation (the "Company"), with the Securities and Exchange
Commission on or about February 25, 2002. The Registration Statement relates to
the proposed sale from time to time pursuant to Rule 415 of the Securities Act
of 1933, as amended (the "Securities Act"), of the following securities of the
Company with an initial aggregate offering price of up to $3,000,000,000 or the
equivalent thereof: (i) senior debt securities (the "Senior Debt Securities");
(ii) subordinated debt securities (the "Subordinated Debt Securities and
collectively with the Senior Debt Securities, the "Debt Securities");
(iii) shares of common stock, $0.01 par value per share (the "Common Stock");
(iv) shares of preferred stock, $0.01 par value per share (the "Preferred
Stock"); (v) depositary shares (the "Depositary Shares") of the Company
representing a fractional interest in a share of Preferred Stock; and/or
(vi) warrants to purchase Debt Securities, Preferred Stock or Common Stock (the
"Warrants") of the Company (the Debt Securities, Common Stock, Preferred Stock,
Depositary Shares and Warrants are collectively referred to herein as the
"Securities"). The Securities are to be sold from time to time as set forth in
the Registration Statement, the Prospectus contained therein (the "Prospectus")
and the supplements to the Prospectus (the "Prospectus Supplements").

    The Senior Debt Securities are to be issued pursuant to a Senior Debt
Securities Indenture entered into between the Company and J.P. Morgan Trust
Company, National Association (formerly known as Chase Manhattan Bank and Trust
Company, National Association) (the "Trustee") and dated as of June 1, 2000 (the
"Senior Indenture"). The form of Senior Indenture is filed as an exhibit to the
Company's registration statement on Form S-3 (file # 333-30786) and incorporated
by reference into the Registration Statement. The Subordinated Debt Securities
are to be issued pursuant to a Subordinated Debt Securities Indenture (the
"Subordinated Indenture" and taken together with the Senior Indentures, the
"Indentures") to be entered into between the Company and the Trustee, the form
of which is filed as an exhibit to the Company's registration statement on
Form S-3 (file # 333-30786) and incorporated by reference into the Registration
Statement. Each of the Indentures may be supplemented in connection with the
issuance any particular series of Debt Securities, by a supplemental indenture
or other appropriate action of the Company creating such series of Debt
Securities.

    The Securities are to be sold pursuant to an underwriting agreement,
purchase agreement, agency agreement or similar agreement (collectively an
"Underwriting Agreement").

    We have examined instruments, documents and records that we deemed relevant
and necessary for the basis of our opinion hereinafter expressed. In such
examination, we have assumed (a) the authenticity of original documents and the
genuineness of all signatures; (b) the conformity to the originals of all
documents submitted to us as copies; (c) the truth, accuracy and completeness of
the information, representations and warranties contained in the records,
documents, instruments and certificates we have
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Hewlett-Packard Company

February 25, 2002

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reviewed; (d) the Registration Statement, and any amendments thereto (including
any post-effective amendments), will have become effective under the Securities
Act; (e) a Prospectus Supplement will have been filed with the Securities and
Exchange Commission describing the Securities offered thereby; (f) all
Securities will be issued and sold in compliance with applicable federal and
state securities laws and in the manner stated in the Registration Statement and
the applicable Prospectus Supplement; (g) a definitive Underwriting Agreement
with respect to any Securities offered will have been duly authorized and
validly executed and delivered by the Company and the other parties thereto
prior to the issuance of the Securities; (h) any securities issuable upon
conversion, exchange, redemption or exercise of any Securities being offered
will be duly authorized, created and, if appropriate, reserved for issuance upon
such conversion, exchange, redemption or exercise and (i) with respect to shares
of Common Stock or Preferred Stock offered, there will be sufficient shares of
Common Stock or Preferred Stock authorized under the Company's certificate of
incorporation, as amended, and not otherwise reserved for issuance.

    Based on such examination, we are of the opinion that:

    1.  With respect to Debt Securities to be issued under either the Senior
Indenture or Subordinated Indenture, when (A) the Trustee is qualified to act as
Trustee under the Senior Indenture or Subordinated Indenture, as applicable,
(B) the Trustee has duly executed and delivered the Subordinated Indenture or
Senior Indenture, as applicable, (C) the Senior Indenture or Subordinated
Indenture, as applicable, has been duly authorized and validly executed and
delivered by the Company to the Trustee; (D) the Senior Indenture or
Subordinated Indenture, as applicable, has been duly qualified under the Trust
Indenture Act of 1939, as amended, (E) the Board of Directors of the Company or
a duly constituted and acting committee thereof (such Board of Directors or
committee, including the Executive Committee of the Board of Directors, being
hereinafter referred to as the "Board") has taken all necessary corporate
action, and appropriate corporate officers of the Company have taken all
appropriate action in accordance with such corporate action to approve the
issuance and terms of such Debt Securities, the terms of the offering thereof
and related matters, and (F) such Debt Securities have been duly executed,
authenticated, issued and delivered in accordance with the provisions of the
Senior Indenture or Subordinated Indenture, as applicable, and the applicable
definitive Underwriting Agreement approved by the Board upon payment of the
consideration therefor provided for therein, such Debt Securities will be
validly issued and will constitute valid and binding obligations of the Company,
enforceable against the Company in accordance with their terms;

    2.  With respect to shares of Preferred Stock, when both (A) the Board has
taken all necessary corporate action to approve the issuance and terms of the
shares of Preferred Stock, the terms of the offering thereof, and related
matters, including the adoption of a Certificate of Amendment relating to such
Preferred Stock (a "Certificate") and the filing of such Certificate with the
Secretary of State of the State of Delaware, and (B) certificates representing
the shares of Preferred Stock have been duly executed, countersigned, registered
and delivered either (i) in accordance with the applicable definitive
Underwriting Agreement approved by the Board upon payment of the consideration
therefor (not less than the par value of the Preferred Stock) provided for
therein or (ii) upon conversion or exercise of such Security pursuant to the
terms and provisions of such Certificate for the consideration approved by the
Board (not less than the par value of the Preferred Stock), then the shares of
Preferred Stock will be validly issued, fully paid and nonassessable;

    3.  With respect to the Depositary Shares, when (A) the Board has taken all
necessary corporate action to approve the issuance and terms of the Depositary
Shares, the terms of the offering thereof, and related matters, including the
adoption of a Certificate relating to the Preferred Stock underlying such
Depositary Shares and the filing of the Certificate with the Secretary of State
of the State of Delaware, (B) the Deposit Agreement (the "Deposit Agreement") or
Agreements relating to the Depositary Shares
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Hewlett-Packard Company

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and the related Depositary Receipts have been duly authorized and validly
executed and delivered by the Company and the Depositary appointed by the
Company, (C) the shares of Preferred Stock underlying such Depositary Shares
have been deposited with a bank or trust company (which meets the requirements
for the Depositary set forth in the Registration Statement) under the applicable
Deposit Agreement, and (D) the Depositary Receipts representing the Depositary
Shares have been duly executed, countersigned, registered and delivered in
accordance with the appropriate Deposit Agreement and the applicable definitive
Underwriting Agreement approved by the Board upon payment of the consideration
therefor provided for therein, the Depositary Shares will be validly issued;

    4.  With respect to shares of Common Stock, when both (A) the Board has
taken all necessary corporate action to approve the issuance of and the terms of
the offering of the shares of Common Stock and related matters and
(B) certificates representing the shares of Common Stock have been duly
executed, countersigned, registered and delivered either (i) in accordance with
the applicable definitive Underwriting Agreement approved by the Board upon
payment of the consideration therefor (not less than the par value of the Common
Stock) provided for therein or (ii) upon conversion or exercise of any other
Security, in accordance with the terms of such Security or the instrument
governing such Security providing for such conversion or exercise as approved by
the Board, for the consideration approved by the Board (not less than the par
value of the Common Stock), then the shares of Common Stock will be validly
issued, fully paid and nonassessable; and

    5.  With respect to the Warrants, when (A) the Board has taken all necessary
corporate action to approve the creation of and the issuance and terms of the
Warrants, the terms of the offering thereof, and related matters, (B) the
Warrant Agreement (the "Warrant Agreement") or Agreements relating to the
Warrants have been duly authorized and validly executed and delivered by the
Company and the Warrant Agent appointed by the Company, and (C) the Warrants or
certificates representing the Warrants have been duly executed, countersigned,
registered and delivered in accordance with the appropriate Warrant Agreement or
Agreements and the applicable definitive Underwriting Agreement approved by the
Board upon payment of the consideration therefor provided for therein, the
Warrants will be validly issued and will constitute valid and binding
obligations of the Company, enforceable against the Company in accordance with
its terms.

    Our opinion that any document is legal, valid and binding is qualified as
to:

        (a) limitations imposed by bankruptcy, insolvency, reorganization,
    arrangement, fraudulent conveyance, moratorium or other laws relating to or
    affecting the rights of creditors generally;

        (b) rights to indemnification and contribution, which may be limited by
    applicable law or equitable principles; and

        (c) general principles of equity, including without limitation, concepts
    of materiality, reasonableness, good faith and fair dealing, and the
    possible unavailability of specific performance or injunctive relief, and
    limitation of rights of acceleration regardless of whether such
    enforceability is considered in a proceeding in equity or at law.

    Attorneys at our firm are admitted to the practice of law in the State of
New York and we express no opinion as to the laws of any other jurisdiction
other than the federal laws of the United States of America and the General
Corporation Law of the State of Delaware.

    We hereby consent to the filing of this opinion as an exhibit to the
above-referenced Registration Statement and to the use of our name wherever it
appears in the Registration Statement, the Prospectus,
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Hewlett-Packard Company

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the Prospectus Supplement, and in any amendment or supplement thereto. In giving
such consent, we do not believe that we are "experts" within the meaning of such
term as used in the Act or the rules and regulations of the Securities and
Exchange Commission issued thereunder with respect to any part of the
Registration Statement, including this opinion as an exhibit or otherwise.

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                                                /s/ Wilson Sonsini Goodrich & Rosati

                                                Wilson Sonsini Goodrich & Rosati
                                                Professional Corporation
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