<PAGE>   1

                                                                  EXHIBIT 10.13


                            SECURED PROMISSORY NOTE


$41,250.00                                                    San Francisco, CA
                                                                 March 21, 1996



        FOR VALUE RECEIVED, the undersigned hereby promises to pay to the order
of Graphix Zone, Inc., 42 Corporate Park, Suite 200, Irvine, California 92174,
or at such other place as the holder of this Note ("Holder") may designate in
writing from time to time, the principal amount of Forty-One Thousand Two
Hundred Fifty Dollars ($41,250.00) together with interest thereon calculated
from the date set forth above until paid at the rate of six percent (6%) per
annum, computed and compounded annually. The entire unpaid principal balance
and accrued interest shall be due and payable on or before termination of
employment with StarPress, Inc. or any successor company (including, without
limitation, Holder or any successor to Holder).  At the option of the Holder,
payments will be applied first to interest, next to any collection charge or
expense and last to reduction of principal.

        The undersigned may prepay all or any portion of the amount due under
this Note without premium or penalty.  Any prepayment shall be applied first to
full payment of accrued interest, next to any collection charge or expense and
last to reduction of principal.

        The undersigned represents and warrants that funds advanced pursuant to
this Note will be used to acquire common stock of StarPress, Inc. Time is of
the essence of this Note and of the payments and performances hereunder and
under any of the other documents executed by the undersigned in connection
herewith. 

        The occurrence of one or more of the following events ("Events of
Default") shall constitute a default under this Note: (i) the failure to pay
principal and interest under this Note when the same shall become due and
payable or (ii) the undersigned's application for consent to or acquiescence in
the appointment of a trustee, receiver, liquidator, assignee, sequestrator or
other similar official for the undersigned or the undersigned's property (or if
involuntary the failure of the undersigned to have the same discharged with 60
days), or the making of a general assignment for the benefit of creditors, or
any bankruptcy, reorganization, debt arrangement or other proceeding under any
bankruptcy or other insolvency law of common law or in equity being instituted
by or against the undersigned (and, only if involuntary, the same is not
dismissed within 60 days).

        Upon the occurrence of an Event of Default, and in addition to any
other right or remedy provided by applicable law, the Holder may without
further demand protest or notice of any kind to the undersigned, declare any
or all sums and obligations due under this Note to be immediately due and
payable, and upon such declaration the same shall become and be immediately due
and payable, the interest rate shall be increased to the lesser of ten percent
(10%) per annum or the maximum interest rate allowed under applicable law, and
interest shall thereafter be added to the principal balance to bear interest
itself.  The undersigned agrees to pay all costs of collection and reasonable
attorney's fees in case of any Event of Default.  The nonexercise by the Holder
of its 


<PAGE>   2
rights hereunder in any particular instance shall not constitute a waiver
thereof in that or any subsequent instance.

        The obligations of this Note shall be joint and several. The
undersigned, and all endorsers and all persons liable or to become liable on
this Note, severally waive diligence, presentment, demand, protest and notice
of demand, protest and nonpayment, and consent to any and all renewals and
extensions of the time of payment hereof.

        This Note shall be governed by and construed in accordance with the
laws of the State of California.


                                        /s/ RONALD S. POSNER
                                        ----------------------------
                                        Ronald S. Posner

                                        Social Security #: ###-##-####
                                                           -----------