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                                                                     EXHIBIT 4.5

THIS CONVERTIBLE SUBORDINATED PROMISSORY NOTE AND THE SECURITIES ISSUABLE
HEREUNDER HAVE BEEN ACQUIRED FOR INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"). SUCH SECURITIES MAY NOT BE
SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION UNLESS THE COMPANY
RECEIVES AN OPINION OF COUNSEL REASONABLY ACCEPTABLE TO THE COMPANY STATING THAT
SUCH SALE OR TRANSFER IS EXEMPT FROM THE REGISTRATION AND PROSPECTUS DELIVERY
REQUIREMENTS OF THE ACT.

                             CARSDIRECT.COM, INC.

                   CONVERTIBLE SUBORDINATED PROMISSORY NOTE

                                                        Sherman Oaks, California
$490,000                                                      September 28, 1999

     FOR VALUE RECEIVED, CarsDirect.com, Inc., a Delaware corporation (the
"Company") hereby promises to pay to GBJ Holdings, a Delaware limited liability
company (the "Holder") the principal sum of Four Hundred Ninety Thousand Dollars
($490,000), plus interest on the unpaid and unconverted principal balance from
the date hereof until paid or converted in accordance with the terms hereof at a
rate of 3% per annum payable on the Maturity Date referred to below, subject to
the terms and provisions below. If (i) the Holder has not converted all
outstanding principal and interest into the Series C Preferred Stock of the
Company in accordance with Section 2 hereof by September 28, 2003 or (ii) the
designee of Holder ("Holder's Designee") ceases to be a director of the Company
by virtue of his/her resignation, his/her decision not to stand for election or
removal for cause, the Company shall be obligated to pay all outstanding
principal and accrued interest on this Promissory Note to Holder on the Maturity
Date. For purposes hereof, the Maturity Date shall mean the earlier of (x)
September 28, 2003, or (y) the date Holder's Designee ceases to be a director of
the Company because of any of the events set forth in clause (ii) above;
furthermore, for purposes hereof, "his/her resignation" and "his/her decision
not to stand for election" shall not include his/her death or permanent
disability.

     This Promissory Note is issued in connection with that certain Series C
Preferred Stock and Note Purchase Agreement, dated as of September 20, 1999 (the
"Purchase Agreement"), by and between the Company and the Holder. All
capitalized terms not otherwise defined herein shall have the meanings ascribed
to them in the Purchase Agreement, unless the context otherwise requires.

     Section 1. Payment. All payments of principal and interest made in
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accordance with this Promissory Note are to be made by check in immediately
available United States funds at the address of the Holder as indicated in the
Purchase Agreement, or at such other address as the Holder may designate from
time to time by written notice to the Company.

     No delay or omission on the part of the Holder in exercising any right
hereunder shall operate as a waiver of such right or any other right of the
Holder, nor shall any delay, omission or waiver of any one occasion be deemed a
bar to or waiver of the same or any other right or any other occasion.
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The Company and every endorser and guarantor of this Promissory Note regardless
of the time, order or place of signing hereby waives presentment, demand,
protest and notice of every kind, and assents to any extension or postponement
of the time for payment or any other indulgence, to any substitution, exchange
or release of collateral, and to the addition or release of any other party or
person or entity primarily or secondarily liable.

     Interest payable under this Promissory Note shall be calculated on the
basis of actual number of days elapsed over a year of 360 days. All payments
received by the Holder hereunder will be applied first to interest and the
balance to principal.

     Section 2. Conversion.

          2.1  Conversion into Preferred Stock. In accordance with the
               -------------------------------
provisions of Section 2.2 hereof, the Holder shall be deemed to have elected to
convert $122,500 of the then unpaid principal amount of this Promissory Note,
together with any accrued but unpaid interest thereon, into Series C Preferred
Stock of the Company upon each of September 28, 2000, September 28, 2001,
September 28, 2002 and September 28, 2003 (each, a "Conversion Date") (unless
the Company receives a written request from the Holder at least 30 days prior to
each such respective Conversion Date that the conversion of such $122,500
principal amount and any accrued but unpaid interest thereon not occur, in which
case the conversion on the applicable Conversion Date or any other Conversion
Date (including as described in the next sentences) will not under any
circumstances occur). On April 30, 2002 (a "Conversion Date") the then entire
unpaid principal amount of this Promissory Note together with any accrued but
unpaid interest thereon, shall be automatically converted into Common Stock of
the Company if prior to April 30, 2000, the Company shall have consummated an
initial public offering pursuant to an effective registration statement under
the Securities Act covering the offer and sale of the Company's Common Stock to
the public with gross proceeds to the Company of not less than $20 million at a
per share price of at least $7.00 (an "IPO") (unless the company receives a
written request from the Holder at least 30 days prior to the closing of such
IPO that such conversion not occur, in which case such conversion will not under
any circumstances occur). If the Company shall have consummated an IPO following
April 30, 2000 and prior to August 31, 2001, then, two years following the
closing of such IPO (a "Conversion Date") the then entire unpaid principal
amount of this Promissory Note together with any accrued but unpaid interest
thereon, shall be automatically converted into Common Stock of the Company
(unless the Company receives a written request from the Holder at least 30 days
prior to such Conversion Date that such conversion not occur, in which case such
conversion will not under any circumstances occur). Any conversion effected
pursuant to this Section 2.1 shall be at a rate which shall be equal to the
quotient obtained by dividing (x) the principal amount of this Promissory Note
and any accrued but unpaid interest by (y) $2.86294 (as adjusted for any
recapitalizations, stock dividends, stock splits and the like) (the "Conversion
Price").

          2.2  Mechanics and Effect of Conversion. No fractional shares of
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Series C Preferred Stock will be issued upon any conversion of this Promissory
Note. In lieu of any fractional share to which the Holder would otherwise be
entitled, the Company will pay to the Holder that amount of the unconverted
amount due under of this Promissory Note in cash. Upon any conversion of this
Promissory Note pursuant to this Section 2, interest on the principal amount of
this Promissory Note so converted shall cease to accrue, and the Company will at
its own expense as soon as practicable

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thereafter, issue and deliver to the Holder, a certificate or certificates for
the number of shares of Series C Preferred Stock to which the Holder is entitled
upon such conversion, together with a check for immediately available funds
payable to the Holder for any cash amounts payable to Holder. Upon conversion of
the entire principal amount of this Promissory Note, the Holder shall surrender
this Promissory Note, duly endorsed, at the principal offices of the Company or
any transfer agent for the Company. At its expense, the Company will, as soon as
practicable thereafter, issue and deliver to the Holder, a certificate or
certificates for the number of shares of Series C Preferred Stock to which the
Holder is entitled upon such conversion, together with a check for immediately
available funds payable to the Holder for any cash amounts payable to Holder.
Upon any conversion of the entire principal amount of, and accrued interest
under, this Promissory Note, the Company will be forever released from all of
its obligations and liabilities under this Promissory Note with regard to the
entire principal amount plus all accrued interest hereunder, including, without
limitation, the obligation to pay such principal amount and accrued interest.

          2.3  Adjustment to Number and Type of Securities and Exercise Price.
               --------------------------------------------------------------
The type and number of securities of the Company issuable upon conversion of
this Promissory Note are subject to adjustment as set forth below:

               (a)  Adjustment for Stock Splits, Stock Dividends,
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Recapitalizations, Conversion, etc. The number and type of securities and/or
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other property issuable upon conversion of this Promissory Note shall be
appropriately and proportionately adjusted to reflect any stock dividend, stock
split, combination of shares, reclassification, recapitalization, (including
without limitation conversion of Series C Preferred Stock to another class of
securities), or other similar event affecting the number or character of
outstanding shares of Series C Preferred Stock, so that the number and type of
securities and/or other property issuable upon conversion of this Promissory
Note shall be equal to that which would have been issuable with respect to the
number of shares of Series C Preferred Stock subject hereto at the time of such
event, had such shares of Series C Preferred Stock then been outstanding.

               (b)  Adjustment for Reorganization, Consolidation, Merger, etc.
                    ---------------------------------------------------------
In case of any consolidation or merger of the Company with or into any other
corporation, entity or person, or any other corporate reorganization, in which
the Company shall not be the continuing or surviving entity of such
consolidation, merger or reorganization (any such transaction being hereinafter
referred to as a "Reorganization"), then, in each case, the Holder of this
Promissory Note, on conversion hereof at any time after the consummation or
effective date of such Reorganization shall receive, in lieu of the Series C
Preferred Stock issuable on such conversion prior to the date of such
Reorganization, the stock and other securities and property (including cash) to
which such holder would have been entitled upon the date of such Reorganization
if such Holder had converted this Promissory Note immediately prior thereto.

     Section 3. Events of Default. If any of the following events shall occur,
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the entire unpaid principal and accrued interest on the Promissory Note shall be
immediately due and payable:

               (a) The institution by the Company of proceedings to be
adjudicated a bankrupt or insolvent, or the consent by it to institution of
bankruptcy or insolvency proceedings against it or the filing by it of a
petition or answer or consent seeking reorganization or release under

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the Federal Bankruptcy Act, or any other applicable federal or state law, or the
consent by it to the filing of any such petition or the appointment of a
receiver, liquidator, assignee, trustee, or other similar official, of the
Company, or of any substantial part of its property, or the making by it of an
assignment for the benefit of creditors, or the admission by it in writing of
its inability to pay its debts generally as they become due or the taking of
corporate action by the Company in furtherance of any such action; or

               (b) If, within sixty (60) days after the commencement of an
action against the Company seeking any bankruptcy, insolvency, reorganization,
liquidation, dissolution or similar relief under any present or future statute,
law or regulation, such action shall not have been dismissed or all orders or
proceedings thereunder affecting the operations or the business of the Company
stayed, or if the stay of any such order or proceeding shall thereafter be set
aside, or if, within sixty (60) days after the appointment without the consent
or acquiescence of the Company of any trustee, receiver or liquidator of the
Company or of all or any substantial part of the properties of the Company, such
appointment shall not have been vacated; or

               (c) The Company fails to pay any principal or interest hereunder
when due pursuant to the terms of this Promissory Note; or

               (d) The Company shall be in material default under the terms of
any other bond, debenture, note or other evidence of indebtedness, which default
shall not have been cured.

     Section 4. Subordination of Indebtedness.
                -----------------------------

          4.1   Subordination. The indebtedness evidenced by this Promissory
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Note is hereby expressly subordinated, to the extent and in the manner
hereinafter set forth, in right of payment to the prior payment in full of all
indebtedness of the Company, or with respect to which the Company is a
guarantor, to banks, commercial finance lenders, insurance companies, leasing or
equipment financing institutions or other lending institutions regularly engaged
in the business of lending money, which is for money borrowed, or purchase or
leasing of equipment in the case of lease or other equipment financing, by the
Company, whether or not secured ("Senior Indebtedness").

          4.2   Further Assurances. By acceptance of this Promissory Note, the
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Holder agrees to execute and deliver customary forms of subordination agreement
requested from time to time by holder(s) of Senior Indebtedness, and as a
condition to the Holder's rights hereunder, Company may require that Holder
execute such forms of subordination agreement.

          4.3   Other Indebtedness. No indebtedness which does not constitute
                ------------------
Senior Indebtedness shall be senior in any respect to the indebtedness
represented by this Promissory Note.

          4.4   Subrogation. Subject to the payment in full of all Senior
                -----------
Indebtedness, the Holder of this Promissory Note shall be subrogated to the
rights of the holder(s) of such Senior Indebtedness (to the extent of the
payments or distributions made to the holder(s) of such Senior Indebtedness
pursuant to the provisions of this Section 4) to receive payments and
distributions of assets of Company applicable to the Senior Indebtedness. For
purposes of such subrogation, no payments or distributions to the holder(s) of
Senior Indebtedness to which the Holder would be

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entitled except for the provisions of this Section 4 shall, as between Company
and its creditors, other than the holder(s) of Senior Indebtedness and the
Holder, be deemed to be a payment by Company to or on account of the Senior
Indebtedness.

          4.5   No Impairment. Subject to the rights, if any, of the holder(s)
                -------------
of Senior Indebtedness under this Section 4 to receive cash, securities or other
properties otherwise payable or deliverable to the Holder of this Promissory
Note and the other restrictions set forth in this Section 4, nothing contained
in this Section 4 shall impair, as between Company and Holder, the obligation of
Company, subject to the terms and conditions hereof, to pay to the Holder the
principal hereof and interest hereon as and when the same become due and payable
or shall prevent the Holder, upon the occurrence of an Event of Default as
described in Section 3 hereof hereunder from exercising all rights, powers and
remedies provided herein or by applicable law.

          4.6   Holder's Waivers. Holder hereby expressly waives for the benefit
                ----------------
of the holder(s) of Senior Indebtedness (i) all notices not specifically
required pursuant to the terms of this Note whatsoever, including without
limitation any notice of the incurrence of Senior Indebtedness; (ii) any claim
which Holder may now or hereafter have against a holder of Senior Indebtedness
arising out of any and all actions which a holder of Senior Indebtedness in good
faith, takes or omits to take with respect to the Senior Indebtedness
(including, without limitation, (A) actions with respect to the creation,
perfection or continuation of liens in or on any collateral security for the
Senior Indebtedness, (B) actions with respect to the occurrence of an event of
default under any Senior Indebtedness, (C) actions with respect to the
foreclosure upon, sale, release, or depreciation of, or failure to realize upon,
any of the collateral security for the Senior Indebtedness and (D) actions with
respect to the collection of any claim for all or any part of the Senior
Indebtedness or the valuation, use, protection or release of any collateral
security for the Senior Indebtedness).

     Section 5. Miscellaneous.
                -------------

          5.1   Titles and Subtitles. The titles and subtitles used herein are
                --------------------
for convenience only and are not to be considered in construing or interpreting
this Promissory Note.

          5.2   Notices. Unless otherwise provided, any notice required or
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permitted under this Promissory Note shall be given in writing and shall be
deemed effectively given upon personal delivery to the party to be notified,
upon delivery by facsimile transmission, or upon the fifth business day after
deposit with the United States Post Office, postage prepaid and addressed to the
party to be notified at the address indicated for such party on the signature
page hereof, or at such other address as such party may designate by ten (10)
days advance written notice to the other party.

          5.3   Highest Lawful Rate. Anything in this Promissory Note to the
                -------------------
contrary notwithstanding, the Company shall never be required to pay interest on
this Promissory Note at a rate in excess of the Highest Lawful Rate (as
hereinafter defined), and if the effective rate of interest which would
otherwise be payable under this Promissory Note would exceed the Highest Lawful
Rate, or if the maturity of this Promissory Note is accelerated for any reason
before the Maturity Date, or in the event of voluntary prepayment by the Company
hereof, or if the Holder shall otherwise receive any unearned interest or shall
receive monies that are deemed to constitute interest which would increase the
effective rate of interest payable under this Promissory Note to a rate in

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excess of the Highest Lawful Rate, then (a) the amount of interest which would
otherwise be payable under this Promissory Note shall be reduced to the amount
allowed under applicable law, and (b) any interest paid by the Company or any
interest paid by the Company in excess of the Highest Lawful Rate shall be
credited to the principal of this Promissory Note. It is further agreed that,
without limitation of the foregoing, all calculations of the rate of interest
contracted for, charged or received by the Holder under this Promissory Note
that are made for the purpose of determining whether such rate exceeds the
Highest Lawful Rate shall be made, to the extent permitted by applicable usury
laws (now or hereafter enacted), by amortizing, prorating and spreading in equal
parts during the period of the full stated term of this Promissory Note all
interest at any time contracted for, charged or received by the Holder in
connection herewith. "Highest Lawful Rate" shall mean the maximum rate of
interest which the Holder is permitted by applicable law to contract for, charge
or receive and as to which the Company could not successfully assert a claim or
defense of usury.

          5.4   Amendments and Waivers. Any term of this Promissory Note may be
                ----------------------
amended and the observance of any term of this Promissory Note may be waived
(either generally or in a particular instance and either retroactively or
prospectively), only with the written consent of the Company and the Holder. Any
amendment or waiver effected in accordance with this subsection 5.4 shall be
binding upon the Holder of this Promissory Note, each future holder of all such
securities and the Company.

          5.5   Severability. If one or more provisions of this Promissory Note
                ------------
are held to be unenforceable under applicable law, such provision shall be
excluded from this Promissory Note, and the remaining provisions of this
Promissory Note shall be interpreted as if such provision were so excluded and
shall be enforceable in accordance with their terms, with the effect of the
excluded provision being taken into consideration and the remaining terms
construed in accordance with the intent of this Promissory Note.

          5.6   Governing Law. This  Promissory Note shall be governed by and
                -------------
construed and enforced in accordance with the internal laws of the State of
California.

                 [Remainder of Page Intentionally Left Blank]

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     IN WITNESS WHEREOF, this Convertible Subordinated Promissory Note has been
duly executed and delivered under its corporate seal as of the date first above
written.

                                        CARSDIRECT.COM, INC.
                                        a Delaware corporation

                                        By:        /s/ Scott Painter
                                            --------------------------------
                                            Name:
                                            Title:

                                        Address: 4312 Woodman Avenue, 3rd Floor
                                                 Sherman Oaks, CA  91423


ACCEPTED AND AGREED


GBJ HOLDINGS, LLC


By:   /s/ Joel S. Beckman
    --------------------------
    Joel S. Beckman
    Member

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