<PAGE>


                                                                  EXHIBIT 4.02.1

                                                                  EXECUTION COPY

                             NOTE PURCHASE AGREEMENT

      This Note Purchase Agreement (the "Agreement") is entered into as of
August 14, 2001 (the "Effective Date") by and between CSK Auto Corporation, a
Delaware corporation (the "Company"), and Oppenheimer Capital Income Fund, a
registered open-end investment company organized as a Massachusetts trust (the
"Purchaser"). Capitalized terms used herein and not otherwise defined herein are
defined in Section 9.11.

      WHEREAS, the Purchaser desires to purchase $30,000,000.00 aggregate
principal amount of the Company's 7% Convertible Subordinated Notes due 2006
(the "Notes") on the terms set forth herein.

      NOW THEREFORE, in consideration of the mutual promises, covenants and
conditions hereinafter set forth, the parties hereto agree as follows:

      1.    AGREEMENT TO PURCHASE AND SELL THE NOTES.

            1.1. Authorization. As of the Closing, the Company will have
authorized the issuance of $30,000,000.00 aggregate principal amount of Notes
for sale hereunder having the rights, preferences, privileges and restrictions
set forth in the form of Note attached to this Agreement as Exhibit A.

            1.2. Agreement to Purchase and Sell the Notes. Subject to the terms
and conditions hereof, on the date of the Closing, the Company will issue and
sell to the Purchaser, and the Purchaser will purchase from the Company, the
Notes at 100% of the principal amount thereof (the "Purchase Price"). The
Purchase Price shall be paid by wire transfer of funds to a designated account
of the Company.

      2.    CLOSING.  The purchase and sale of the Notes hereunder shall be
held at the offices of the Company, on August 14, 2001, or at such other time
and place as the Company and the Purchaser may mutually agree upon (the
"Closing").

      3.    COMPANY REPRESENTATIONS AND WARRANTIES.  The Company hereby
represents and warrants to the Purchaser that the statements in this Section
3 are and will be true and correct in all material respects on the date
hereof and on the Closing Date:

            3.1. Organization. The Company and each Subsidiary is a corporation
duly organized, validly existing and in good standing under, and by virtue of,
the laws of their respective jurisdiction of incorporation and each has all
requisite corporate power and authority to own its properties and assets and to
carry on its business as now conducted and as presently proposed to be
conducted. The Company has heretofore made available to the Purchaser accurate
and complete copies of its Certificate of Incorporation and Bylaws, as currently
in full force and effect.


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            3.2. Capitalization. The authorized capital stock of the Company
consists of a total of 50,000,000 authorized shares of Common Stock ($0.01 par
value) of which 27,842,105 shares were issued and outstanding as of August 13,
2001. All of the outstanding shares of Common Stock have been validly issued and
are fully paid, nonassessable and free of preemptive rights. As of May 6, 2001,
approximately 3,378,000 shares of Common Stock were available for issuance under
the Company's option plans, of which approximately 2,990,000 were issuable upon
or otherwise deliverable in connection with the exercise of options outstanding
on such date. Between May 6, 2001 and the date hereof, no shares of the
Company's capital stock have been issued other than pursuant to stock options
and warrants already in existence on such date and except for grants of stock
options to employees, officers and directors in the ordinary course of business
consistent with past practice.

            3.3. Due Authorization and Adoption. All action on the part of the
Company, its officers and directors necessary for the authorization, execution
and delivery of, and the performance of all obligations of the Company under,
this Agreement, the authorization, issuance and delivery of the Notes, and the
authorization, issuance, reservation for issuance and delivery of all the
4,524,886 shares of Common Stock into which the Notes are convertible (the
"Conversion Shares") has been taken or will be taken prior to the Closing. This
Agreement is a valid and binding obligation of the Company enforceable in
accordance with its terms, subject, as to enforcement of remedies, to applicable
bankruptcy, insolvency, moratorium, reorganization and similar laws affecting
creditors' rights generally and to general equitable principles.

            3.4.  Valid Issuance of Stock.  The shares of Common Stock, when
issued and delivered in accordance with the terms of the Notes, will be duly
and validly issued, and will be fully paid and non assessable.

            3.5. Company SEC Reports. The Company has filed all required forms,
reports and documents (the "Company Reports") with the Securities and Exchange
Commission (the "SEC") since January 1, 1999, each of which, complied at the
time of filing in all material respects with all applicable requirements of the
Securities Act and the Exchange Act, as in effect on the respective dates such
forms, reports and documents were filed. None of such Company Reports, including
any financial statements or schedules included or incorporated by reference
therein, contained when filed any untrue statement of a material fact or omitted
to state a material fact required to be stated or incorporated by reference
therein or necessary in order to make the statements therein in light of the
circumstances under which they were made not misleading, except to the extent
superseded by a Company Report filed subsequently and prior to the date hereof.
The audited consolidated financial statements of the Company included in the
Company Reports were prepared in accordance with generally accepted accounting
principles (except, in the case of unaudited consolidated quarterly statements,
as permitted by Form 10-Q of the SEC, applied on a consistent basis during the
period involved, except as may otherwise be indicated in the notes thereto) and
fairly present, in conformity in all material respects with applicable
accounting requirements and published rules and regulations of the SEC, the
consolidated financial position of the Company and its consolidated subsidiaries
as of the dates thereof and the consolidated results of their operations and
cash flows for the periods then ended (subject, in the case of unaudited
quarterly statements, to normal year-end audit adjustments).


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      4.    REPRESENTATIONS AND WARRANTIES OF THE PURCHASER.  The Purchaser
represents and warrants to the Company as follows:

            4.1. Authorization. This Agreement when executed and delivered by
the Purchaser will constitute a valid and legally binding obligation of the
Purchaser, subject, as to enforcement of remedies, to applicable bankruptcy,
insolvency, moratorium, reorganization and similar laws affecting creditors'
rights generally and to general equitable principles.

            4.2. Investigation; Economic Risk; Accredited Investor. The
Purchaser acknowledges that it has had an opportunity to discuss the business,
affairs and current prospects of the Company with its officers. The Purchaser
further acknowledges having had access to all information about the Company that
it has requested. The Purchaser acknowledges that it is able to fend for itself
in the transactions contemplated by this Agreement and has the ability to bear
the economic risks of its investment pursuant to this Agreement. The Purchaser
is an "accredited investor" as such term is defined in Rule 501 of the
Securities Act.

            4.3.  Purchase for Own Account.  The Notes and the Conversion
Shares will be acquired for its own account, not as a nominee or agent, and
not with a view to or in connection with the sale or distribution of any part
thereof.

            4.4. Exempt from Registration; Restricted Securities. The Purchaser
understands that the Notes and the Conversion Shares (subject to the
Registration Rights Agreement) will not be registered under the Securities Act,
on the ground that the sale provided for in this Agreement is exempt from
registration under the Securities Act, and that the reliance of the Company on
such exemption is predicated in part on the Purchaser's representations set
forth in this Agreement. The Purchaser understands that the Notes and the
Conversion Shares (subject to the Registration Rights Agreement) being purchased
hereunder are restricted securities within the meaning of Rule 144 under the
Securities Act and must be held indefinitely unless their sale is subsequently
registered under the Securities Act or an exemption from such registration is
available.

            4.5.  Restrictive Legends.  It is understood that each
certificate representing the Notes and, when issued, the Conversion Shares,
shall be stamped or otherwise imprinted with a legend substantially in the
following form:

      THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
      SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR UNDER THE SECURITIES
      LAWS OF ANY STATES. THESE SECURITIES ARE SUBJECT TO RESTRICTIONS ON
      TRANSFERABILITY AND RESALE AND MAY NOT BE TRANSFERRED OR RESOLD EXCEPT AS
      PERMITTED UNDER THE ACT AND THE APPLICABLE STATE SECURITIES LAWS, PURSUANT
      TO REGISTRATION OR EXEMPTION THEREFROM. INVESTORS SHOULD BE AWARE THAT
      THEY MAY BE REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS INVESTMENT FOR AN
      INDEFINITE PERIOD OF TIME. THE ISSUER OF THESE SECURITIES MAY REQUIRE AN
      OPINION OF COUNSEL IN FORM AND SUBSTANCE


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      REASONABLY SATISFACTORY TO THE ISSUER TO THE EFFECT THAT ANY PROPOSED
      TRANSFER OR RESALE IS IN COMPLIANCE WITH THE ACT AND ANY APPLICABLE
      STATE SECURITIES LAWS.

            4.6 Removal of Restrictive Legend. The legend set forth above shall
be removed by the Company from any certificate evidencing Notes or Conversion
Shares upon delivery to the Company of an opinion by counsel, reasonably
satisfactory to the Company, that a registration statement under the Act is at
that time in effect with respect to the legended security or that such security
can be freely transferred in a public sale without such a registration statement
being in effect and that such transfer will not jeopardize the exemption or
exemptions from registration pursuant to which the Company issued the Notes.

      5.    COVENANTS OF THE COMPANY.  The Company covenants to the Purchaser
as follows:

            5.1 Use of Proceeds. The Company will use the proceeds from the sale
of the Notes to make a loan to CSK Auto, Inc.

            5.2 Listing of Shares. The Company will as promptly as practical
list and keep listed on the New York Stock Exchange, upon official notice of
issuance, all shares of Common Stock issuable upon conversion of the Notes for
so long as the Common Stock continues to be so listed.


      6.    CONDITIONS TO THE PURCHASER'S OBLIGATIONS AT THE CLOSING.  The
obligation of the Purchaser to purchase the Notes at the Closing is subject
to the fulfillment, to the satisfaction of the Purchaser on or prior to the
Closing, of the following conditions:

            6.1. Representations and Warranties Correct. The representations and
warranties made by the Company in Section 3 hereof shall be true and correct
when made, and shall be true and correct as of the date of Closing with the same
force and effect as if they had been made on and as of such date, subject to
changes contemplated by this Agreement.

            6.2. Performance of Obligations. The Company shall have performed
and complied with all agreements, obligations and conditions contained in this
Agreement that are required to be performed or complied with by it on or before
the Closing and shall have obtained all approvals, consents and qualifications
necessary to complete the purchase and sale described herein.

            6.3. Proceedings and Documents. All corporate and other proceedings
in connection with the transactions contemplated hereby and all documents and
instruments incident to such transactions shall be satisfactory in substance and
form to the Purchaser, and the Purchaser shall have received all such
counterpart originals or certified or other copies of such documents as it may
reasonably request.

            6.4.  Notes.  The Company shall have delivered to the Purchaser a
certificate representing the Notes purchased by the Purchaser.
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            6.5.  Registration Rights Agreement.  The Company shall have
executed and delivered the Registration Rights Agreement in substantially the
form attached hereto as Exhibit B.

            6.6.  Compliance Certificate.  At the Closing, the Company shall
deliver to the Purchaser a certificate, dated the date of Closing, signed by
the Company's President certifying that the conditions specified in Sections
6.1, 6.2 and 6.3 have been fulfilled.

      7.    CONDITIONS TO COMPANY'S OBLIGATIONS AT THE CLOSING.  The
obligations of the Company under this Agreement are subject to the
fulfillment at or before the Closing of the following conditions:

            7.1.  Representations and Warranties.  The representations and
warranties of the Purchaser contained in Section 4 hereof shall be true as of
the Closing.

            7.2.  Payment of Purchase Price.  The Purchaser shall have
delivered to the Company the Purchase Price in accordance with the provisions
of Section 2.


      8.    TERMINATION.

            8.1.  Termination.  This Agreement may be terminated at any time
prior to the Closing:

                  (a)   by mutual written consent of the Purchaser and the
Company;

                  (b) by the Purchaser or the Company if (1) any court of
competent jurisdiction or other Government Authority, shall have issued a final
order, decree or ruling, or taken any other final action, restraining, enjoining
or otherwise prohibiting the consummation of this Agreement and such order,
decree, ruling or other action is or shall have become nonappealable or (2) this
Agreement has not been consummated by August 31, 2001 (the "Final Date");
provided, however, that no party may terminate this Agreement pursuant to this
Subsection (b) if such party's failure to fulfill any of its obligations under
this Agreement shall have been a principal reason that the Closing shall not
have occurred on or before said date;

                  (c) by the Company if there shall have been a material breach
of any representations or warranties on the part of the Purchaser set forth in
this Agreement or if any representations or warranties of the Purchaser shall
have become untrue in any material respect, such that the conditions set forth
in Section 7 would be incapable of being satisfied by the Final Date, provided
that the Company has not breached any of its obligations hereunder in any
material respect; or

                  (d) by the Purchaser if (1) there shall have been a material
breach of any representations or warranties on the part of the Company set forth
in this Agreement or if any representations or warranties of the Company shall
have become untrue in any material respect, such that the conditions set forth
in Section 6 would be incapable of being satisfied by the Final Date, provided
that the Purchaser has not breached any of its obligations hereunder in any


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material respect; (2) there shall have been a breach by the Company of one or
more of its covenants or agreements in this Agreement in any material respect or
materially adversely affecting (or materially delaying) the ability of the
Purchaser or the Company to consummate this Agreement, and the Company has not
cured such breach within ten (10) business days after notice by the Purchaser
thereof, provided that the Purchaser has not breached any of its obligations
hereunder in any material respect.

            8.2. Effect of Termination. Upon the termination and abandonment of
this Agreement pursuant to Section 8.1, this Agreement shall forthwith become
void and have no effect without any liability on the part of any party hereto or
its affiliates, directors, officers or shareholders other than as set forth in
this Section 8.2. Nothing contained in this Section 8.2 shall relieve any party
from liability for any breach of this Agreement prior to such termination and in
such event the breaching party shall remain liable for the consequences of such
breach following termination.

            8.3. Extension; Waiver. At any time prior to the Closing, each party
hereto may, only by action taken in writing, (i) extend the time for the
performance of any of the obligations or other acts of the other party, (ii)
waive any inaccuracies in the representations and warranties of the other party
contained herein or in any document certificate or writing delivered pursuant
hereto or (iii) waive compliance by the other party with any of the agreements
or conditions contained herein. Any agreement on the part of any party hereto to
any such extension or waiver shall be valid only if set forth in an instrument,
in writing, signed on behalf of such party. The failure of any party hereto to
assert any of its rights hereunder shall not constitute a waiver of such rights.


      9.    MISCELLANEOUS.

            9.1. Governing Law and Jurisdiction. This Agreement shall be
governed in all respects by the laws of the State of Delaware without regard to
provisions regarding choice of laws. The parties hereto hereby submit to the
non-exclusive jurisdiction of the federal and Delaware State courts located in
the City of Dover in connection with any dispute related to this letter or any
matters contemplated hereby.

            9.2.  Survival.  The representations, warranties, covenants and
agreements made herein shall survive any investigation made by any party
hereto and the closing of the transactions contemplated hereby.

            9.3. Successors and Assigns. Except as otherwise expressly provided
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors and administrators of the
parties hereto whose rights or obligations hereunder are affected by such
amendments. This Agreement and the rights and obligations therein may not be
assigned by the Purchaser without the written consent of the Company except to
an affiliate of the Purchaser. This Agreement and the rights and obligations
therein may not be assigned by the Company without the written consent of the
Purchaser.


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            9.4. Entire Agreement. This Agreement and the schedules and exhibits
hereto which are hereby expressly incorporated herein by this reference, with
the form of Note attached hereto as Exhibit A and the Registration Rights
Agreement attached hereto as Exhibit B, constitute the entire understanding and
agreement between the parties with regard to the subjects hereof and thereof;
provided, however, that nothing in this Agreement shall be deemed to terminate
or supersede the provisions of any confidentiality and nondisclosure agreements
executed by the parties hereto prior to the date of the Closing, which
agreements shall continue in full force and effect until terminated in
accordance with their respective terms.

            9.5. Notices. Except as may be otherwise provided herein, all
notices, requests, waivers and other communications made pursuant to this
Agreement shall be in writing and shall be conclusively deemed to have been duly
given (a) when hand delivered to the other party; (b) when received when sent by
facsimile at the address and number set forth below; (c) three (3) business days
after deposit in the U.S. mail with first class or certified mail receipt
requested postage prepaid and addressed to the other party as set forth below;
or (d) the next business day after deposit with a national overnight delivery
service, postage prepaid, addressed to the parties as set forth below with
next-business-day delivery guaranteed, provided that the sending party receives
a confirmation of delivery from the delivery service provider.


      CSK Auto, Inc.                         Oppenheimer Capital Income Fund
      645 E. Missouri Avenue                 Two World Trade Center
      Phoenix, Arizona  85012                New York, New York  10048
      Attn.:  Lon B. Novatt, Esq.            Attn.: Michael S. Levine
      Telecopier No.:  (602) 264-0495        Telecopier No.:

      with a copy to:                        with a copy to:

      Gibson, Dunn & Crutcher LLP            Oppenheimer Capital Income Fund
      1801 California Street                 Two World Trade Center
      Denver, Colorado  80202                New York, New York  10048
      Attn.:  Richard M. Russo, Esq.         Attn.: Katherine P. Feld
      Telecopier No.:  (303) 298-5715        Telecopier No.: (212) 321-1159


            Each person making a communication hereunder by facsimile shall
promptly confirm by telephone to the person to whom such communication was
addressed each communication made by it by facsimile pursuant hereto but the
absence of such confirmation shall not affect the validity of any such
communication. A party may change or supplement the addresses given above, or
designate additional addresses, for purposes of this Section 9.5 by giving the
other party written notice of the new address in the manner set forth above.

            9.6.  Amendments and Waivers.  Any term of this Agreement may be
amended only with the written consent of the Company and the Purchaser.


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            9.7. Delays or Omissions. No delay or omission to exercise any
right, power or remedy accruing to the Company or to the Purchaser, upon any
breach or default of any party hereto under this Agreement, shall impair any
such right, power or remedy of the Company, or the Purchaser nor shall it be
construed to be a waiver of any such breach or default, or an acquiescence
therein, or of any similar breach of default thereafter occurring; nor shall any
waiver of any other breach or default theretofore or thereafter occurring. Any
waiver, permit, consent or approval of any kind or character on the part of the
Company or the Purchaser of any breach of default under this Agreement or any
waiver on the part of the Company or the Purchaser of any provisions or
conditions of this Agreement, must be in writing and shall be effective only to
the extent specifically set forth in such writing. All remedies, either under
this Agreement, or by law or otherwise afforded to the Company or the Purchaser
shall be cumulative and not alternative.

            9.8.  Titles and Subtitles.  The titles of the sections and
subsections of this Agreement are for convenience of reference only and are
not to be considered in construing this Agreement.

            9.9.  Counterparts.  This Agreement may be executed in any number
of counterparts, each of which shall be an original, but all of which
together shall constitute one instrument.

            9.10. Severability.  Should any provision of this Agreement be
determined to be illegal or unenforceable, such determination shall not
affect the remaining provisions of this Agreement.

            9.11  Certain Definitions.  For the purposes of this Agreement
the term:

      "Agreement" is defined in the Preamble.

      "affiliate" shall mean, as to any specified Person, any other Person that,
directly or indirectly through one or more intermediaries or otherwise,
controls, is controlled by or is under common control with the specified Person.
As used in this definition, "control" means the possession, directly or
indirectly, of the power to direct or cause the direction of the management or
policies of a Person (whether through ownership of capital stock of that Person,
by contract or otherwise).

      "Closing" is defined in Section 2.1.

      "Common Stock" shall mean the Company's common stock, par value $0.01 per
share.

      "Company" means CSK Auto Corporation, a Delaware corporation.

      "Conversion Shares" is defined in Section 3.4.

      "Exchange Act" means the Securities Exchange Act of 1934, as amended.


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      "Material Adverse Effect" shall mean any material adverse effect on the
financial condition, business or operations of the Company and its Subsidiaries
taken as a whole.

      "NYSE" means the New York Stock Exchange.

      "Person" shall mean any natural person, entity, estate, trust, union or
employee organization or government agency or subdivision thereof.

      "Purchase Price" shall have the meaning in Section 1.2.


      "SEC"  The term "SEC" or "Commission" means the U.S. Securities and
Exchange Commission.

      "Securities Act" means the Securities Act of 1933, as amended.

      "Subsidiary" means, with respect to any Person, any corporation,
association or other entity of which more than 50% of the total voting power of
shares of stock or other equity interests (without regard to the occurrence of
any contingency) to vote in the election of directors, managers or trustees
thereof is, at the time as of which any determination is being made, owned or
controlled, directly or indirectly, by such Person or one or more of its
Subsidiaries, or both. The term "Subsidiary" or "Subsidiaries" when used herein
without reference to any particular Person, means a Subsidiary or Subsidiaries
of the Company.



                           [SIGNATURE PAGE FOLLOWS]


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      IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the day and year herein above first written.

                                    CSK AUTO CORPORATION,

                                    By:   /s/ Don W. Watson
                                          ------------------------------
                                    Name: Don W. Watson
                                    Title:SR VP CFO


                                    OPPENHEIMER CAPITAL INCOME FUND

                                    By:   /s/ Michael S. Levine
                                          ------------------------------------
                                    Name: Michael S. Levine
                                    Title:Vice President