<PAGE>

                                                                   Exhibit 10.37

                                   DDi Corp.
                         EMPLOYEE STOCK PURCHASE PLAN


SECTION 1.  PURPOSE OF PLAN
            ---------------

     The DDi Corp. Employee Stock Purchase Plan (the "Plan") is intended to
provide a method by which eligible employees of DDi Corp. and such of its
Subsidiaries as the Board of Directors of DDi Corp. (the "Board of Directors")
may from time to time designate (DDi Corp. and such Subsidiaries being
hereinafter referred to as the "Company") may use voluntary, systematic payroll
deductions to purchase shares of common stock, $.01 par value of DDi Corp. (such
common stock being hereafter referred to as "Stock") and thereby acquire an
interest in the future of DDi Corp.  For purposes of the Plan, a "Subsidiary" is
any corporation that would be treated as a subsidiary of DDi Corp. under Section
424(f) of the Internal Revenue Code of 1986, as amended (the "Code").  The Plan
is intended to qualify under Section 423 of the Code and shall be construed
accordingly.

SECTION 2.  OPTIONS TO PURCHASE STOCK
            -------------------------

     Under the Plan, there is available an aggregate of not more than 1,450,000
shares of Stock (subject to adjustment as provided in Section 15) for sale
pursuant to the exercise of options ("Options") granted under the Plan to
employees of the Company ("Employees") who meet the eligibility requirements set
forth in Section 3 hereof ("Eligible Employees").  The Stock to be delivered
upon exercise of Options under the Plan may be either shares of authorized but
unissued Stock or shares of reacquired Stock, as the Board of Directors may
determine.

SECTION 3.  ELIGIBLE EMPLOYEES
            ------------------

     Except as otherwise provided below, each Employee who has completed six
months of employment for the Company will be eligible to participate in the
Plan.

     (a)  Any Employee who immediately after the grant of an Option would own
(or pursuant to Section 423(b)(3) of the Code would be deemed to own) stock
possessing 5% or more of the total combined voting power or value of all classes
of stock of the employer corporation or of its parent or subsidiary
corporations, as defined in Section 424 of the Code, will not be eligible to
receive an Option to purchase Stock pursuant to the Plan.
<PAGE>

     (b)  No Employee will be granted an Option under the Plan that would permit
his or her rights to purchase shares of stock under all employee stock purchase
plans of the employer corporation and parent and subsidiary corporations to
accrue at a rate which exceeds $25,000 in fair market value of such stock
(determined at the time the Option is granted) for each calendar year during
which any such Option granted to such Employee is outstanding at any time, as
provided in Section 423 of the Code.

     (c)  The following categories of Employees shall not be eligible to
participate in the Plan: (i) Employees whose customary employment for the
Company is twenty (20) hours or less per week, (ii) Employees whose customary
employment for the Company is for not more than five (5) months in any calendar
year.

SECTION 4.  METHOD OF PARTICIPATION
            -----------------------

     The periods January 1 to June 30 and July 1 to December 31 of each year
will be termed "Option Periods"; provided, however, that the first Option Period
shall commence on the date of the final prospectus for the DDi Corp.'s initial
public offering and shall terminate on June 30, 2000. Each person who will be an
Eligible Employee on the first day of any Option Period may elect to participate
in the Plan by executing and delivering, at least 15 days prior to such day, a
payroll deduction authorization in accordance with Section 5. Such Employee will
thereby become a participant ("Participant") on the first day of such Option
Period and will remain a Participant until his or her participation is
terminated as provided in the Plan.

SECTION 5.  PAYROLL DEDUCTION
            -----------------

     The payroll deduction authorization will request withholding at a rate (in
whole percentages) up to 10% from the Participant's Compensation by means of
substantially equal payroll deductions over the Option Period from payroll
periods ending in the Option Period.  For purposes of the Plan, "Compensation"
means all base straight time gross earnings plus payments for overtime, shift
premiums, commissions and bonuses, but excluding all incentive income, incentive
payments, awards, or other compensation. A Participant may change the
withholding rate of his or her payroll deduction authorization by written notice
delivered to the Company at least 15 days prior to the first day of the Option
Period as to which the change is to be effective. All amounts withheld in
accordance with a Participant's payroll deduction authorization will be credited
to a withholding account maintained in the Participant's name on the books of
the Company.  Amounts credited to the withholding account shall belong to the
Company and shall not be required to be set aside in trust or otherwise
segregated from the Company's general assets.

                                      -2-
<PAGE>

SECTION 6.  GRANT OF OPTIONS
            ----------------

     Each person who is a Participant on the first day of an Option Period will
be granted, as of such day and for such Period, an Option entitling the
Participant to acquire a whole number of shares of Stock equal in number to the
lesser of:

          (a)  the whole number (disregarding any fractional share amount)
     determined by dividing $12,500.00 by the fair market value of one share of
     Stock on the first day of the Option Period; and

          (b)  the whole number (disregarding any fractional share amount)
     determined by dividing (i) the balance credited to the Participant's
     withholding account on the last day of the Option Period, by (ii) the
     purchase price per share of the Stock determined under Section 7.

DDi Corp. will reduce, on a substantially proportionate basis, the number of
shares of Stock purchasable by each Participant upon exercise of his or her
Option for an Option Period in the event that the number of shares then
available under the Plan is insufficient.  Option grants under this Section 6
shall be automatic and need not be separately documented.

SECTION 7.  PURCHASE PRICE
            --------------

     The purchase price of Stock issued pursuant to the exercise of an Option
will be 85% of the fair market value of the Stock at (a) the time of grant of
the Option or (b) the time at which the Option is deemed exercised, whichever is
less.  Fair market value will mean the Closing Price of the Stock.  The "Closing
Price" of the Stock on any business day will be the last sale price, regular
way, with respect to such Stock, or, in case no such sale takes place on such
day, the average of the closing bid and asked prices, regular way, with respect
to such Stock, in either case as reported in the principal consolidated
transaction reporting system with respect to securities listed or admitted to
trading on the Nasdaq National Market or the Nasdaq SmallCap Market of the
Nasdaq Stock Market; or, if such Stock is not listed or admitted to trading on
the Nasdaq National Market or the Nasdaq SmallCap Market of the Nasdaq Stock
Market, as reported in the principal consolidated transaction reporting system
with respect to securities listed on the principal national securities exchange
on which such Stock is listed or admitted to trading; or, if such Stock is not
listed or admitted to trading, the last quoted price with respect to such Stock,
or, if not so quoted, the average of the high bid and low asked prices in the
over-the-counter market with respect to such Stock, as reported by the National
Association of Securities Dealers, Inc. Automated Quotation System or such other
similar system then in use; or, if on any such date such Stock is not quoted by
any such organization, the average of the closing bid and asked prices with
respect to such Stock, as furnished by a professional market maker making a
market in such Stock selected by the Board of Directors

                                      -3-
<PAGE>

in good faith; or, if no such market maker is available, the fair market value
of such Stock as of such day as determined in good faith by the Board of
Directors.

SECTION 8.  EXERCISE OF OPTIONS
            -------------------

     If any Employee is a Participant in the Plan on the last business day of an
Option Period, he or she will be deemed to have exercised the Option granted to
him or her for that Period. Upon such exercise, the Company will apply the
balance of the Participant's withholding account to the purchase of the whole
number of shares of Stock determined under Section 6 and as soon as practicable
thereafter will issue and deliver, or cause to be issued and delivered, said
shares to the Participant and will return to him or her the balance, if any, of
his or her withholding account in excess of the total purchase price of the
shares so issued; provided, that if the balance left in the account consists
solely of an amount equal to the value of a fractional share it will be retained
in the Account and carried over to the next Period.

     No fractional shares will be issued to the Participant.  Notwithstanding
anything herein to the contrary, DDi Corp.'s obligation to issue and deliver
shares of Stock under the Plan will be subject to the approval required of any
governmental authority in connection with the authorization, issuance, sale or
transfer of said shares, to any requirements of any national securities exchange
applicable thereto, and to compliance by DDi Corp. with other applicable legal
requirements in effect from time to time.

SECTION 9.  INTEREST
            --------

     No interest will be payable on withholding accounts.

SECTION 10. CANCELLATION AND WITHDRAWAL
            ---------------------------

     A Participant who holds an Option under the Plan may at any time prior to
exercise thereof under Section 8 cancel all (but not less than all) of his or
her Options by written notice delivered to the Company.  Upon such cancellation,
the balance in the Participant's withholding account will be returned to the
Participant.

     A Participant may terminate his or her payroll deduction authorization as
of any date by written notice delivered to the Company and will thereby cease to
be a Participant as of such date.  Any Participant who voluntarily terminates
his or her payroll deduction authorization prior to the last business day of an
option period will be deemed to have canceled his or her Option.

                                      -4-
<PAGE>

SECTION 11.  TERMINATION OF EMPLOYMENT
             -------------------------

     Except as otherwise provided in Section 12, upon the termination of a
Participant's employment with the Company for any reason, he or she will cease
to be a Participant, any Option held by him or her under the Plan will be deemed
canceled, the balance of his or her withholding account will be returned, and he
or she will have no further rights under the Plan.

SECTION 12.  DEATH OF PARTICIPANT
             --------------------

     In the event a Participant's service with the Company is terminated by
reason of death occurring prior to the last day of an Option Period, any Options
then held by the Participant shall be deemed forthwith canceled in accordance
with Section 10. The balance of the deceased Participant's withholding account
shall be delivered to the Participant's designated beneficiary(ies). For
purposes of the Plan, a Participant's designated beneficiary(ies), if any, shall
be such person or persons on file with the Company or its designated agent, on a
form approved by the Company or its designated agents, as the Participant's
designated beneficiary(ies). If the Participant has more than one designated
beneficiary, the Company will determine the allocation among them and its
determination will be final and binding on all persons. If there is no
designated beneficiary or if the designated beneficiary(ies) are not living, the
Company shall instead deliver the account balance to the executor or
administrator of the estate of the Participant, if the Company is able to
identify such executor or administrator. If the Company is unable to identify
such executor or administrator, the Company, in its discretion, may deliver such
account balance to the spouse or to any one or more dependents of a Participant
as the Company may determine. No beneficiary will, prior to the death of the
Participant, acquire any interest in amounts credited to he Participant under
the Plan.

SECTION 13.  EQUAL RIGHTS; PARTICIPANT'S RIGHTS NOT TRANSFERABLE
             ---------------------------------------------------

     All Participants granted Options under the Plan with respect to any Option
Period will have the same rights and privileges. Each Participant's rights and
privileges under any Option granted under the Plan will be exercisable during
the Participant's lifetime only by him or her and may not be sold, pledged,
assigned, or transferred in any manner. In the event any Participant violates or
attempts to violate the terms of this Section, any Options held by him or her
may be terminated by the Company and, upon return to the Participant of the
balance of his or her withholding account, all of the Participant's rights under
the Plan will terminate.

                                      -5-
<PAGE>

SECTION 14.  EMPLOYMENT RIGHTS
             -----------------

     Nothing contained in the provisions of the Plan will be construed as giving
to any Employee the right to be retained in the employ of the Company or as
interfering with the right of the Company to discharge any Employee at any time.

SECTION 15.  CHANGE IN CAPITALIZATION
             ------------------------

     In the event of any change in the outstanding Stock of DDi Corp. by reason
of a stock dividend, split-up, recapitalization, merger, consolidation,
reorganization, or other capital change, the aggregate number and type of shares
available under the Plan, the number and type of shares under Options granted
but not exercised, the maximum number and type of shares purchasable under an
Option, and the Option price will be appropriately adjusted.

SECTION 16.  ADMINISTRATION OF PLAN
             ----------------------

     The Plan will be administered by the Board of Directors, which will have
the right to determine any questions which may arise regarding the
interpretation and application of the provisions of the Plan and to make,
administer, and interpret such rules and regulations as it will deem necessary
or advisable. The Board of Directors may in its discretion delegate one or more
of its responsibilities to any committee or person. Reference to the Board of
Directors in connection with its administrative function under the Plan shall
include its delegates.

SECTION 17.  AMENDMENT AND TERMINATION OF PLAN
             ---------------------------------

     DDi Corp. reserves the right at any time or times to amend the Plan to any
extent and in any manner it may deem advisable, by vote of the Board of
Directors; provided, that any amendment that would be treated as the adoption of
a new plan for purposes of Section 423 of the Code and the regulations
thereunder will have no force or effect unless approved by the shareholders of
DDi Corp. within twelve months before or after its adoption.

     The Plan may be suspended or terminated at any time by the Board of
Directors. In connection therewith, the Board of Directors may either cancel
outstanding Options or continue them and provide that they will be exercisable
either at the end of the applicable Option Period as determined under Section 4
above or on such earlier date as the Board of Directors may specify (in which
case such earlier date shall be treated as the last day of the applicable Option
Period).

                                      -6-
<PAGE>

SECTION 18.  APPROVAL OF SHAREHOLDERS
             ------------------------

     The Plan and the ability to exercise Options granted hereunder will be
subject to the approval of the shareholders of DDi Corp. obtained within twelve
months before or after the date the Plan is adopted by the Board of Directors.

                                      -7-