<PAGE>

                                                                     EXHIBIT 4.1


                                  CORIO, INC.

                         2001 NONSTATUTORY STOCK PLAN


     1.   Purposes of the Plan. The purposes of this Nonstatutory Stock Plan
          --------------------
are:

           .  to attract and retain the best available personnel for positions
              of substantial responsibility,

           .  to provide additional incentive to Employees, Directors and
              Consultants, and

           .  to promote the success of the Company's business.

           Options granted under the Plan will be Nonstatutory Stock Options.
     Stock Purchase Rights may also be granted under the Plan.

     2.   Definitions. As used herein, the following definitions shall apply:
          -----------

     (a)     "Administrator" means the Board or any of its Committees as shall
              -------------
be administering the Plan, in accordance with Section 4 of the Plan.

     (b)     "Applicable Laws" means the requirements relating to the
              ---------------
administration of stock option plans under U.S. state corporate laws, U.S.
federal and state securities laws, the Code, any stock exchange or quotation
system on which the Common Stock is listed or quoted and the applicable laws of
any foreign country or jurisdiction where Options or Stock Purchase Rights are,
or will be, granted under the Plan.

     (c)     "Board" means the Board of Directors of the Company.
              -----

     (d)     "Code" means the Internal Revenue Code of 1986, as amended.
              ----

     (e)     "Committee" means a committee of Directors appointed by the Board
              ---------
in accordance with Section 4 of the Plan.

     (f)     "Common Stock" means the Common Stock of the Company.
              ------------

     (g)     "Company" means Corio, Inc., a Delaware corporation.
              -------
<PAGE>

     (h)     "Consultant" means any person, including an advisor, engaged by the
              ----------
Company or a Parent or Subsidiary to render services to such entity.

     (i)     "Director" means a member of the Board.
              --------

     (j)     "Disability" means total and permanent disability as defined in
              ----------
Section 22(e)(3) of the Code.

     (k)     "Employee" means any person, including Officers, employed by the
              --------
Company or any Parent or Subsidiary of the Company. A Service Provider shall not
cease to be an Employee in the case of (i) any leave of absence approved by the
Company or (ii) transfers between locations of the Company or between the
Company, its Parent, any Subsidiary, or any successor. Neither service as a
Director nor payment of a director's fee by the Company shall be sufficient to
constitute "employment" by the Company.

     (l)     "Exchange Act" means the Securities Exchange Act of 1934, as
              ------------
amended.

     (m)     "Fair Market Value" means, as of any date, the value of Common
              -----------------
Stock determined as follows:

               (i)    If the Common Stock is listed on any established stock
exchange or a national market system, including without limitation the Nasdaq
National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market, its
Fair Market Value shall be the closing sales price for such stock (or the
closing bid, if no sales were reported) as quoted on such exchange or system for
the last market trading day prior to the time of determination, as reported in
The Wall Street Journal or such other source as the Administrator deems
reliable;

               (ii)   If the Common Stock is regularly quoted by a recognized
securities dealer but selling prices are not reported, the Fair Market Value of
a Share of Common Stock shall be the mean between the high bid and low asked
prices for the Common Stock on the last market trading day prior to the day of
determination, as reported in The Wall Street Journal or such other source as
the Administrator deems reliable;

               (iii)  In the absence of an established market for the Common
Stock, the Fair Market Value shall be determined in good faith by the
Administrator.

     (n)     "Notice of Grant" means a written or electronic notice evidencing
              ---------------
certain terms and conditions of an individual Option grant or Stock Purchase
Right. The Notice of Grant is part of the Option Agreement.

     (o)     "Officer" means a person who is an officer of the Company within
              -------
the meaning of Section 16 of the Exchange Act and the rules and regulations
promulgated thereunder.

                                      -2-
<PAGE>

     (p)     "Option" means a nonstatutory stock option granted pursuant to the
              ------
Plan, that is not intended to qualify as an incentive stock option within the
meaning of Section 422 of the Code and the regulations promulgated thereunder.

     (q)     "Option Agreement" means an agreement between the Company and an
              ----------------
Optionee evidencing the terms and conditions of an individual Option grant. The
Option Agreement is subject to the terms and conditions of the Plan.

     (r)     "Option Exchange Program" means a program whereby outstanding
              -----------------------
options are surrendered in exchange for options with a lower exercise price.

     (s)     "Optioned Stock" means the Common Stock subject to an Option or
              --------------
Stock Purchase Right.

     (t)     "Optionee" means the holder of an outstanding Option or Stock
              --------
Purchase Right granted under the Plan.

     (u)     "Parent" means a "parent corporation," whether now or hereafter
              ------
existing, as defined in Section 424(e) of the Code.

     (v)     "Plan" means this 2001 Nonstatutory Stock Plan.
              ----

     (w)     "Restricted Stock" means shares of Common Stock acquired pursuant
              ----------------
to a grant of Stock Purchase Rights under Section 11 of the Plan.

     (x)     "Restricted Stock Purchase Agreement" means a written agreement
              -----------------------------------
between the Company and the Optionee evidencing the terms and restrictions
applying to stock purchased under a Stock Purchase Right. The Restricted Stock
Purchase Agreement is subject to the terms and conditions of the Plan and the
Notice of Grant.

     (y)     "Service Provider" means an Employee including an Officer,
              ----------------
Consultant or Director.

     (z)     "Share" means a share of the Common Stock, as adjusted in
              -----
accordance with Section 13 of the Plan.

     (aa)    "Stock Purchase Right" means the right to purchase Common Stock
              --------------------
pursuant to Section 11 of the Plan, as evidenced by a Notice of Grant.

     (bb)    "Subsidiary" means a "subsidiary corporation," whether now or
              ----------
hereafter existing, as defined in Section 424(f) of the Code.

      3.   Stock Subject to the Plan. Subject to the provisions of Section 13 of
          -------------------------
the Plan, the maximum aggregate number of Shares which may be optioned and sold
under the Plan is Three Million (3,000,000) Shares. The Shares may be
authorized, but unissued, or reacquired Common Stock.

                                      -3-
<PAGE>

           If an Option or Stock Purchase Right expires or becomes
unexercisable without having been exercised in full, or is surrendered pursuant
to an Option Exchange Program, the unpurchased Shares which were subject thereto
shall become available for future grant or sale under the Plan (unless the Plan
has terminated); provided, however that Shares that have actually been issued
under the Plan, whether upon exercise of an Option or Stock Purchase Right,
shall not be returned to the Plan and shall not become available for future
distribution under the Plan, except that if Shares of Restricted Stock are
repurchased by the Company at their original purchase price, such Shares shall
become available for future grant under the Plan.

     4.   Administration of the Plan.
          --------------------------

     (a)     Administration. The Plan shall be administered by (i) the Board or
             --------------
(ii) a Committee, which committee shall be constituted to satisfy Applicable
Laws.

     (b)     Powers of the Administrator. Subject to the provisions of the Plan,
             ---------------------------
and in the case of a Committee, subject to the specific duties delegated by the
Board to such Committee, the Administrator shall have the authority, in its
discretion:

               (i)    to determine the Fair Market Value of the Common Stock;

               (ii)   to select the Service Providers to whom Options and Stock
Purchase Rights may be granted hereunder;

               (iii)  to determine whether and to what extent Options and Stock
Purchase Rights are granted hereunder;

               (iv)   to determine the number of shares of Common Stock to be
covered by each Option and Stock Purchase Right granted hereunder;

               (v)    to approve forms of agreement for use under the Plan;

               (vi)   to determine the terms and conditions, not inconsistent
with the terms of the Plan, of any award granted hereunder. Such terms and
conditions include, but are not limited to, the exercise price, the time or
times when Options or Stock Purchase Rights may be exercised (which may be based
on performance criteria), any vesting acceleration or waiver of forfeiture
restrictions, and any restriction or limitation regarding any Option or Stock
Purchase Right or the shares of Common Stock relating thereto, based in each
case on such factors as the Administrator, in its sole discretion, shall
determine;

               (vii)  to reduce the exercise price of any Option or Stock
Purchase Right to the then current Fair Market Value if the Fair Market Value of
the Common Stock covered by such Option or Stock Purchase Right shall have
declined since the date the Option or Stock Purchase Right was granted;

               (viii) to institute an Option Exchange Program;

                                      -4-
<PAGE>

               (ix)   to construe and interpret the terms of the Plan and awards
granted pursuant to the Plan;

               (x)    to prescribe, amend and rescind rules and regulations
relating to the Plan, including rules and regulations relating to sub-plans
established for the purpose of qualifying for preferred tax treatment under
foreign tax laws;

               (xi)   to modify or amend each Option or Stock Purchase Right
(subject to Section 15(b) of the Plan), including the discretionary authority to
extend the post-termination exercisability period of Options longer than is
otherwise provided for in the Plan;

               (xii)  to authorize any person to execute on behalf of the
Company any instrument required to effect the grant of an Option or Stock
Purchase Right previously granted by the Administrator;

               (xiii) to determine the terms and restrictions applicable to
Options or Stock Purchase Rights;

               (xiv)  to allow Optionees to satisfy withholding tax obligations
by electing to have the Company withhold from the Shares to be issued upon
exercise of an Option or Stock Purchase Right that number of Shares having a
Fair Market Value equal to the amount required to be withheld. The Fair Market
Value of the Shares to be withheld shall be determined on the date that the
amount of tax to be withheld is to be determined. All elections by an Optionee
to have Shares withheld for this purpose shall be made in such form and under
such conditions as the Administrator may deem necessary or advisable; and

               (xv)   to make all other determinations deemed necessary or
advisable for administering the Plan.

     (c)     Effect of Administrator's Decision. The Administrator's decisions,
             ----------------------------------
determinations and interpretations shall be final and binding on all Optionees
and any other holders of Options or Stock Purchase Rights.

     5.   Eligibility. Options and Stock Purchase Rights may be granted to
          -----------
Service Providers.

     6.   Limitation. Neither the Plan nor any Option or Stock Purchase Right
          ----------
shall confer upon an Optionee any right with respect to continuing the
Optionee's relationship as a Service Provider with the Company, nor shall they
interfere in any way with the Optionee's right or the Company's right to
terminate such relationship at any time, with or without cause.

     7.   Term of Plan. The Plan shall become effective upon its adoption by the
          ------------
Board.  It shall continue in effect for ten (10) years, unless sooner terminated
under Section 15 of the Plan.

     8.   Term of Option. The term of each Option shall be stated in the Option
          --------------
Agreement.

                                      -5-
<PAGE>

      9.  Option Exercise Price and Consideration.
          ---------------------------------------
     (a)       Exercise Price. The per share exercise price for the Shares to be
               --------------
issued pursuant to exercise of an Option shall be determined by the
Administrator.

     (b)       Waiting Period and Exercise Dates. At the time an Option is
               ---------------------------------
granted, the Administrator shall fix the period within which the Option may be
exercised and shall determine any conditions which must be satisfied before the
Option may be exercised.

     (c)       Form of Consideration. The Administrator shall determine the
               ---------------------
acceptable form of consideration for exercising an Option, including the method
of payment. Such consideration may consist entirely of:

                    (i)    cash;

                    (ii)   check;

                    (iii)  promissory note;

                    (iv)   other Shares which (A) in the case of Shares acquired
upon exercise of an option, have been owned by the Optionee for more than six
months on the date of surrender, and (B) have a Fair Market Value on the date of
surrender equal to the aggregate exercise price of the Shares as to which said
Option shall be exercised;

                    (v)    consideration received by the Company under a
cashless exercise program implemented by the Company in connection with the
Plan;

                    (vi)   a reduction in the amount of any Company liability to
the Optionee, including any liability attributable to the Optionee's
participation in any Company-sponsored deferred compensation program or
arrangement;

                    (vii)   such other consideration and method of payment for
the issuance of Shares to the extent permitted by Applicable Laws; or

                    (viii)  any combination of the foregoing methods of payment.

     10.  Exercise of Option.
          ------------------

     (a)       Procedure for Exercise; Rights as a Stockholder. Any Option
               -----------------------------------------------
granted hereunder shall be exercisable according to the terms of the Plan and at
such times and under such conditions as determined by the Administrator and set
forth in the Option Agreement. Unless the Administrator provides otherwise,
vesting of Options granted hereunder shall be tolled during any unpaid leave of
absence. An Option may not be exercised for a fraction of a Share.

               An Option shall be deemed exercised when the Company receives:
(i) written or electronic notice of exercise (in accordance with the Option
Agreement) from the person entitled

                                      -6-
<PAGE>

to exercise the Option, and (ii) full payment for the Shares with respect to
which the Option is exercised. Full payment may consist of any consideration and
method of payment authorized by the Administrator and permitted by the Option
Agreement and the Plan. Shares issued upon exercise of an Option shall be issued
in the name of the Optionee or, if requested by the Optionee, in the name of the
Optionee and his or her spouse. Until the Shares are issued (as evidenced by the
appropriate entry on the books of the Company or of a duly authorized transfer
agent of the Company), no right to vote or receive dividends or any other rights
as a stockholder shall exist with respect to the Optioned Stock, notwithstanding
the exercise of the Option. The Company shall issue (or cause to be issued) such
Shares promptly after the Option is exercised. No adjustment will be made for a
dividend or other right for which the record date is prior to the date the
Shares are issued, except as provided in Section 13 of the Plan.

               Exercising an Option in any manner shall decrease the number of
Shares thereafter available, both for purposes of the Plan and for sale under
the Option, by the number of Shares as to which the Option is exercised.

     (b)   Termination of Relationship as a Service Provider. If an Optionee
           -------------------------------------------------
ceases to be a Service Provider, other than upon the Optionee's death or
Disability, the Optionee may exercise his or her Option, but only within such
period of time as is specified in the Option Agreement, and only to the extent
that the Option is vested on the date of termination (but in no event later than
the expiration of the term of such Option as set forth in the Option Agreement).
In the absence of a specified time in the Option Agreement, the Option shall
remain exercisable for three (3) months following the Optionee's termination.
If, on the date of termination, the Optionee is not vested as to his or her
entire Option, the Shares covered by the unvested portion of the Option shall
revert to the Plan. If, after termination, the Optionee does not exercise his or
her Option within the time specified by the Administrator, the Option shall
terminate, and the Shares covered by such Option shall revert to the Plan.

     (c)   Disability of Optionee. If an Optionee ceases to be a Service
           ----------------------
Provider as a result of the Optionee's Disability, the Optionee may exercise his
or her Option within such period of time as is specified in the Option
Agreement, to the extent the Option is vested on the date of termination (but in
no event later than the expiration of the term of such Option as set forth in
the Option Agreement). In the absence of a specified time in the Option
Agreement, the Option shall remain exercisable for twelve (12) months following
the Optionee's termination. If, on the date of termination, the Optionee is not
vested as to his or her entire Option, the Shares covered by the unvested
portion of the Option shall revert to the Plan. If, after termination, the
Optionee does not exercise his or her Option within the time specified herein,
the Option shall terminate, and the Shares covered by such Option shall revert
to the Plan.

     (d)   Death of Optionee. If an Optionee dies while a Service Provider, the
           -----------------
Option may be exercised within such period of time as is specified in the Option
Agreement (but in no event later than the expiration of the term of such Option
as set forth in the Notice of Grant), by the Optionee's estate or by a person
who acquires the right to exercise the Option by bequest or inheritance, but
only to the extent that the Option is vested on the date of death. In the
absence of a specified time in

                                      -7-
<PAGE>

the Option Agreement, the Option shall remain exercisable for twelve (12) months
following the Optionee's termination. If, at the time of death, the Optionee is
not vested as to his or her entire Option, the Shares covered by the unvested
portion of the Option shall immediately revert to the Plan. The Option may be
exercised by the executor or administrator of the Optionee's estate or, if none,
by the person(s) entitled to exercise the Option under the Optionee's will or
the laws of descent or distribution. If the Option is not so exercised within
the time specified herein, the Option shall terminate, and the Shares covered by
such Option shall revert to the Plan.

     (e)    Buyout Provisions. The Administrator may at any time offer to buy
            -----------------
out for a payment in cash or Shares, an Option previously granted based on such
to the Optionee at the time that such offer is made.

     11.    Stock Purchase Rights.
            ---------------------

     (a)       Rights to Purchase. Stock Purchase Rights may be issued either
               ------------------
alone, in addition to, or in tandem with other awards granted under the Plan
and/or cash awards made outside of the Plan. After the Administrator determines
that it will offer Stock Purchase Rights under the Plan, it shall advise the
offeree in writing or electronically, by means of a Notice of Grant, of the
terms, conditions and restrictions related to the offer, including the number of
Shares that the offeree shall be entitled to purchase, the price to be paid, and
the time within which the offeree must accept such offer. The offer shall be
accepted by execution of a Restricted Stock Purchase Agreement in the form
determined by the Administrator.

     (b)       Repurchase Option. Unless the Administrator determines otherwise,
               -----------------
the Restricted Stock Purchase Agreement shall grant the Company a repurchase
option exercisable upon the voluntary or involuntary termination of the
purchaser's service with the Company for any reason (including death or
Disability). The purchase price for Shares repurchased pursuant to the
Restricted Stock Purchase Agreement shall be the original price paid by the
purchaser and may be paid by cancellation of any indebtedness of the purchaser
to the Company. The repurchase option shall lapse at a rate determined by the
Administrator.

     (c)       Other Provisions. The Restricted Stock Purchase Agreement shall
               ----------------
contain such other terms, provisions and conditions not inconsistent with the
Plan as may be determined by the Administrator in its sole discretion.

     (d)       Rights as a Stockholder. Once the Stock Purchase Right is
               -----------------------
exercised, the purchaser shall have the rights equivalent to those of a
stockholder, and shall be a stockholder when his or her purchase is entered upon
the records of the duly authorized transfer agent of the Company. No adjustment
will be made for a dividend or other right for which the record date is prior to
the date the Stock Purchase Right is exercised, except as provided in Section 13
of the Plan.

     12.  Non-Transferability of Options and Stock Purchase Rights.  Unless
          --------------------------------------------------------
determined otherwise by the Administrator, an Option or Stock Purchase Right may
not be sold, pledged, assigned, hypothecated, transferred, or disposed of in any
manner other than by will or by the laws of descent or distribution and may be
exercised, during the lifetime of the Optionee, only by the Optionee.  If

                                      -8-
<PAGE>

the Administrator makes an Option or Stock Purchase Right transferable, such
Option or Stock Purchase Right shall contain such additional terms and
conditions as the Administrator deems appropriate.

     13.  Adjustments Upon Changes in Capitalization, Dissolution, Merger or
          ------------------------------------------------------------------
Asset Sale.
----------

     (a)       Changes in Capitalization.  Subject to any required action by the
               -------------------------
stockholders of the Company, the number of shares of Common Stock covered by
each outstanding Option, and the number of shares of Common Stock which have
been authorized for issuance under the Plan but as to which no Options or Stock
Purchase Rights have yet been granted or which have been returned to the Plan
upon cancellation or expiration of an Option or Stock Purchase Right, as well as
the price per share of Common Stock covered by each such outstanding Option or
Stock Purchase Right, shall be proportionately adjusted for any increase or
decrease in the number of issued shares of Common Stock resulting from a stock
split, reverse stock split, stock dividend, combination or reclassification of
the Common Stock, or any other increase or decrease in the number of issued
shares of Common Stock effected without receipt of consideration by the Company;
provided, however, that conversion of any convertible securities of the Company
shall not be deemed to have been "effected without receipt of consideration."
Such adjustment shall be made by the Board, whose determination in that respect
shall be final, binding and conclusive. Except as expressly provided herein, no
issuance by the Company of shares of stock of any class, or securities
convertible into shares of stock of any class, shall affect, and no adjustment
by reason thereof shall be made with respect to, the number or price of shares
of Common Stock subject to an Option or Stock Purchase Right.

     (b)       Dissolution or Liquidation. In the event of the proposed
               --------------------------
dissolution or liquidation of the Company, the Administrator shall notify each
Optionee as soon as practicable prior to the effective date of such proposed
transaction. The Administrator in its discretion may provide for an Optionee to
have the right to exercise his or her Option until ten (10) days prior to such
transaction as to all of the Optioned Stock covered thereby, including Shares as
to which the Option would not otherwise be exercisable. In addition, the
Administrator may provide that any Company repurchase option applicable to any
Shares purchased upon exercise of an Option or Stock Purchase Right shall lapse
as to all such Shares, provided the proposed dissolution or liquidation takes
place at the time and in the manner contemplated. To the extent it has not been
previously exercised, an Option or Stock Purchase Right will terminate
immediately prior to the consummation of such proposed action.

     (c)       Merger or Asset Sale. In the event of a merger of the Company
               --------------------
with or into another corporation, or the sale of substantially all of the assets
of the Company, each outstanding Option and Stock Purchase Right shall be
assumed or an equivalent option or right substituted by the successor
corporation or a Parent or Subsidiary of the successor corporation. In the event
that the successor corporation refuses to assume or substitute for the Option or
Stock Purchase Right, the Optionee shall fully vest in and have the right to
exercise the Option or Stock Purchase Right as to all of the Optioned Stock,
including Shares as to which it would not otherwise be vested or exercisable. If
an Option or Stock Purchase Right becomes fully vested and exercisable in lieu
of assumption or substitution in the event of a merger or sale of assets, the
Administrator shall notify

                                      -9-
<PAGE>

the Optionee in writing or electronically that the Option or Stock Purchase
Right shall be fully vested and exercisable for a period of fifteen (15) days
from the date of such notice, and the Option or Stock Purchase Right shall
terminate upon the expiration of such period. For the purposes of this
paragraph, the Option or Stock Purchase Right shall be considered assumed if,
following the merger or sale of assets, the option or right confers the right to
purchase or receive, for each Share of Optioned Stock subject to the Option or
Stock Purchase Right, immediately prior to the merger or sale of assets, the
consideration (whether stock, cash, or other securities or property) received in
the merger or sale of assets by holders of Common Stock for each Share held on
the effective date of the transaction (and if holders were offered a choice of
consideration, the type of consideration chosen by the holders of a majority of
the outstanding Shares); provided, however, that if such consideration received
in the merger or sale of assets is not solely common stock of the successor
corporation or its Parent, the Administrator may, with the consent of the
successor corporation, provide for the consideration to be received upon the
exercise of the Option or Stock Purchase Right, for each Share of Optioned Stock
subject to the Option or Stock Purchase Right, to be solely common stock of the
successor corporation or its Parent equal in fair market value to the per share
consideration received by holders of Common Stock in the merger or sale of
assets.

     14.  Date of Grant.  The date of grant of an Option or Stock Purchase Right
          -------------
shall be, for all purposes, the date on which the Administrator makes the
determination granting such Option or Stock Purchase Right, or such other later
date as is determined by the Administrator.  Notice of the determination shall
be provided to each Optionee within a reasonable time after the date of such
grant.

     15.  Amendment and Termination of the Plan.
          -------------------------------------

     (a)       Amendment and Termination. The Board may at any time amend,
               -------------------------
alter, suspend or terminate the Plan.

     (b)       Effect of Amendment or Termination. No amendment, alteration,
               ----------------------------------
suspension or termination of the Plan shall impair the rights of any Optionee,
unless mutually agreed otherwise between the Optionee and the Administrator,
which agreement must be in writing and signed by the Optionee and the Company.
Termination of the Plan shall not affect the Administrator's ability to exercise
the powers granted to it hereunder with respect to options granted under the
Plan prior to the date of such termination.

     16.  Conditions Upon Issuance of Shares.
          ----------------------------------

     (a)       Legal Compliance. Shares shall not be issued pursuant to the
               ----------------
exercise of an Option or Stock Purchase Right unless the exercise of such Option
or Stock Purchase Right and the issuance and delivery of such Shares shall
comply with Applicable Laws and shall be further subject to the approval of
counsel for the Company with respect to such compliance.

     (b)       Investment Representations. As a condition to the exercise of an
               --------------------------
Option or Stock Purchase Right the Company may require the person exercising
such Option or Stock Purchase Right to represent and warrant at the time of any
such exercise that the Shares are being purchased

                                      -10-
<PAGE>

only for investment and without any present intention to sell or distribute such
Shares if, in the opinion of counsel for the Company, such a representation is
required.

     17.  Inability to Obtain Authority.  The inability of the Company to obtain
          -----------------------------
authority from any regulatory body having jurisdiction, which authority is
deemed by the Company's counsel to be necessary to the lawful issuance and sale
of any Shares hereunder, shall relieve the Company of any liability in respect
of the failure to issue or sell such Shares as to which such requisite authority
shall not have been obtained.

     18.  Reservation of Shares. The Company, during the term of this Plan, will
          ---------------------
at all times reserve and keep available such number of Shares as shall be
sufficient to satisfy the requirements of the Plan.

                                      -11-