<PAGE>

                                                                    Exhibit 4.02


PREFERRED STOCK                                                  PREFERRED STOCK
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
     NUMBER                                                        SHARES
--------------------------------------------------------------------------------
      RA               eROOM SYSTEM TECHNOLOGIES, INC.

--------------------------------------------------------------------------------
     INCORPORATED UNDER THE LAWS                        SEE REVERSE FOR
       OF THE STATE OF NEVADA                         CERTAIN DEFINITIONS
                                                       CUSIP 296016 20 7
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
            THIS CERTIFIES THAT





            is the record holder of


--------------------------------------------------------------------------------
FULLY PAID AND NONASSESSABLE SHARES OF SERIES A CONVERTIBLE PREFERRED STOCK,
PAR VALUE $.001 PER SHARE, OF
--------------------------------------------------------------------------------
eRoom System Technologies, Inc.
--------------------------------------------------------------------------------
transferable on the books of the Corporation by the registered holder hereof in
person or by duly authorized attorney upon surrender of this Certificate
properly endorsed and upon payment of any applicable taxes. This Certificate is
not valid unless countersigned and registered by the Transfer Agent and
Registrar.
--------------------------------------------------------------------------------
WITNESS the facsimile seal of the Corporation and the facsimile signatures of
its duly authorized officers.
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
         Dated:
--------------------------------------------------------------------------------

                        eROOM SYSTEM TECHNOLOGIES, INC..
                                    CORPORATE
                                      SEAL
                                     NEVADA
 SECRETARY                                                 CHAIRMAN OF THE BOARD
--------------------------------------------------------------------------------
 COUNTERSIGNED AND REGISTERED:
      AMERICAN STOCK TRANSFER & TRUST COMPANY
                TRANSFER AGENT AND REGISTRAR
 BY             AUTHORIZED SIGNATURE

<PAGE>


     THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
  THE SECURITIES ACT OF 1933 (THE "ACT") OR ANY STATE SECURITIES LAWS AND MAY
  NOT BE OFFERED, SOLD, TRANSFERRED, PLEDGED OR HYPOTHECATED IN THE ABSENCE OF
  ANY EFFECTIVE REGISTRATION STATEMENT AS TO SUCH SECURITIES FILED UNDER THE
  ACT, OR ANY EXEMPTION FROM REGISTRATION, AND COMPLIANCE WITH APPLICABLE STATE
  SECURITIES LAWS. THE ISSUER MAY REQUIRE AN OPINION OF COUNSEL SATISFACTORY TO
  THE ISSUER THEREOF THAT SUCH REGISTRATIONS NOT REQUIRED AND THAT SUCH LAWS ARE
  COMPLIED WITH.

    The Corporation will furnish to any stockholder, upon request and without
  charge, a statement of the powers, designations, preferences and relative,
  participating, optional or other special rights of each class of stock or
  series thereof and the qualifications. limitations or restrictions of such
  preferences and /or rights, so far as the same shall have been fixed, and of
  the authority of the Board of Directors to designate and fix any preferences,
  rights and limitations of any wholly unissued series. Any such request should
  be addresses to the Secretary of the Corporation at its corporate
  headquarters.

                         Notice of Election to Convert

    The undersigned hereby irrevocably exercises the rights to convert shares of
  Series A Convertible Preferred Stock represented by this Certificate into
  Common Stock of eRoom System Technologies, Inc. in accordance with the terms
  of the Series A Convertible Preferred Stock relating thereto.

Date: __________________________  Signature(s)________________________________

    KEEP THIS CERTIFICATE IN A SAFE PLACE. IF IT IS LOST, STOLEN, OR DESTROYED
  THE CORPORATION WILL REQUIRE A BOND OF INDEMNITY AS A CONDITION TO THE
  ISSUANCE OF A REPLACEMENT CERTIFICATE.

    The following abbreviations, when used in the inscription the face of this
  certificate, shall be construed as though they were written out in full
  according to applicable laws or regulations:

<TABLE>
<CAPTION>
<S>          <C>

  ---------------------------------------------------------------------------------------------------
  TEN COM      -as tenants in common         UNIF  GIFT MIN ACT              Custodian

  ---------------------------------------------------------------------------------------------------
  TEN ENT      -as tenants by the entireties                      (Cust)                  (Minor)

  ---------------------------------------------------------------------------------------------------
  JT TEN       -as joint tenants                               under Uniform Gifts to Minors
                with right of                --------------------------------------------------------
                survivorship and                               Act
                not as tenants               --------------------------------------------------------
                in common                                                  (State)
  ---------------------------------------------------------------------------------------------------
                                             UNIF TRF MIN ACT                Custodian (until age)

  ---------------------------------------------------------------------------------------------------
                                                                  (Cust)
  ---------------------------------------------------------------------------------------------------
                                                                              under Uniform Transfers

  ---------------------------------------------------------------------------------------------------
                                                                 (Minor)
  ---------------------------------------------------------------------------------------------------
                                                               to Minors Act

  ---------------------------------------------------------------------------------------------------
                                                                                          (State)
  ---------------------------------------------------------------------------------------------------
</TABLE>

    Additional abbreviations may also be used though not in the above list.

FOR THE VALUE RECEIVED, ___________________hereby sell, assign and transfer unto


  ----------------------------------------
     PLEASE INSERT SOCIAL SECURITY OR
                   OTHER
      IDENTIFYING NUMBER OF ASSIGNEE
  ----------------------------------------


  ------------------------------------------------------------------------------
  (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)


  ------------------------------------------------------------------------------

  ------------------------------------------------------------------------------
                                                                         Shares

  ------------------------------------------------------------------------------
      of the Common Stock represented by the within Certificate, and do hereby
      irrevocable constitute and appoint

                                                                        Attorney
  ------------------------------------------------------------------------------
    to transfer the said stock on the books of the within named Corporation with
    full power of substitution in the premises.

    Dated_________________________

                                     X_______________________________

                                     X_______________________________


                        NOTICE:      THE  SIGNATURE(S) TO THIS ASSIGNMENT MUST
                                     CORRESPOND  WITH THE NAME(S) WRITTEN UPON
                                     THE  FACE  OF THE  CERTIFICATE  IN  EVERY
                                     PARTICULAR,    WITHOUT    ALTERATION   OR
                                     ENLARGEMENT OR ANY CHANGE WHATEVER.

  Signature(s) Guaranteed

  -----------------------------------------------

                                       2
<PAGE>

    By

  -----------------------------------------------
    THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION
    (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH
    MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT
    TO S.E.C. RULE 17Ad-15.

  -----------------------------------------------


                                        3