Exhibit 10-51

Lease Agreement with Fortunato Development

This RIDER "D" dated March 30,  2000  annexed to and forming a part of the Lease
Agreement  dated June 30,  1997,  by and  between  Fortunato  Development,  Inc.
(hereinafter referred to as Landlord) and Network Peripherals, Inc.
(hereinafter referred to as Tenant)

Whereas  Landlord and Tenant entered into a Lease Agreement dated June 30, 1997,
in which  Landlord  leased to Tenant and Tenant leased from Landlord the Demised
Premises  known as Suite 102,  in a  building  known as 4170  Veterans  Memorial
Highway, Bohemia, NY 11716, (hereinafter referred to as the Building);

Whereas,  Landlord and Tenant wish to modify the following information contained
herein this Rider "D",

1.   Expansion / Extension / Relocation  Area - Tenant shall lease from Landlord
     the entire second (2nd) floor of the building  called One Corporate  Drive,
     Bohemia  (hereinafter  referred  to  as  the  "new  building").  This  deal
     represents  a lease  term  extension  and a lease  expansion,  as well as a
     tenant relocation.

2.   Size - The  Rentable  Square  Feet (RSF) of the entire 2nd floor of the new
     building is 24,096 RSF.

3.   New Suite  Designation  - The suite name in the new  building is Suite #201
     (hereinafter referred to as the "new suite")

4.   Extension  Term  Period  - The  current  lease,  and all of its  provisions
     (except  as  outlined  herein)  shall  be  extended  so that  the  tenant's
     occupancy in the new suite in the new building shall be seven (7) years.

5.   Existing Space Obligation - As soon as the tenant moves into the new suite,
     in the new building,  the  remaining  obligation to pay rent for the spaces
     leased by Tenant in 4170 Veterans  Memorial  Highway  shall cease.  At that
     point, the tenant shall have rights to occupy only the new suite in the new
     building and the rent  described  herein shall  supercede the rent from the
     original  base lease.  The old suites  shall be vacated  and all  materials
     shall  be  removed  and the old  suites  shall  be  left in  "broom  clean"
     condition.

6.   First  Year  Rent  Structure  - The  rent  for  the new  suite,  in the new
     building,  for the first year will be Four Hundred Twenty Six Thousand Four
     Hundred Ninety Nine Dollars and Twenty Cents  ($426,499.20).  This is based
     on the following breakdown:  The base rent for 75% of the new suite (18,072
     RSF) is $18.00.  Then $.70 per RSF for  cleaning is added and $1.25 per RSF
     for Heating  Ventilating  and Air  Conditioning  (HVAC) gas and electric is
     added.  This brings the rent for 75% of the new suite,  per RSF, to $19.95.
     Then the base rent for the  remaining  25% of the RSF (6,024  RSF) is $9.00
     per RSF plus $.70 for cleaning plus $1.25 per RSF for HVAC gas and electric
     for a total of $10.95 per RSF.

7.   Tenant  Electrical  Service - The tenant's  electric service for lights and
     outlets shall be fed off of a new electrical service. The tenant shall make
     an  application  for this electric  service to Long Island Power  Authority
     (LIPA) and shall pay the utility company directly for the electric consumed
     on this new electric service.

8.   Annual  Escalation - Commencing the 2nd year, and each year  thereafter for
     the balance of the extension  period,  the rent,  cleaning and HVAC gas and
     electric shall be escalated four percent (4%) per year cumulative above the
     previous years total rent amount.

9.   2nd Year  Rent  Structure  & Taxes - The rent for the 2nd year of the lease
     extension,  expansion  and  relocation  shall be Four  Hundred  Ninety Nine
     Thousand Nine Hundred Ninety Two Dollars and No Cents  ($499,992.00),  plus
     pro-rata  share of any tax  increase  over the base year  taxes for the new
     building.  The tax base year shall be the 1999-2000 tax year. Any increases
     in taxes shall be paid by tenants on a pro-rata basis.

10.  New Suite Signage - The tenant shall only be allowed, at tenant's sole cost
     and expense,  suite entrance signage.  Such signage shall be limited to the
     company logo and company name and shall be located  either on a wall within
     the new suite's  reception area or on the entrance door to the new suite on
     the 2nd floor.  A single line  company name and suite number and floor will
     be provided by Landlord on the 1st floor lobby of the new building.

11.  Security  Deposit - The Tenant shall pay the Landlord an additional  sum of
     Fifty Seven  Thousand  One Hundred  Eighty Five Dollars and Forty Six Cents
     ($57,185.46) to add to their existing security deposit.

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<PAGE>

Exhibit 10-51

Lease Agreement with Fortunato Development

12.  Extension Term Commencement  Date - The extension period  commencement date
     shall be  determined  once the Landlord  has  received the signed  original
     copies of this lease  Rider D, the  security  deposit and has signed off on
     the set of designed drawings. The Landlord will use its best efforts to get
     the tenant into the new suite as soon as possible.

13.  Existing  Signage -The Tenant shall make  arrangements to have the tenant's
     building signage removed from the building known as 4170 Veterans  Memorial
     Highway,   Bohemia  and  to  have  the  electric   service  in  suite  #204
     disconnected  from  the  service  in  suite  #102  and  reconnected  to the
     building's house electrical service.

14.  Cleaning - Cleaning shall be provided by Landlord for the new suite and the
     building.

15.  Shared  Build  Out Cost - Once the  Landlord  and the  Tenant  have come to
     agreement  on the  scope  of work to be done in the new  suite,  in the new
     building,  the Landlord shall do a cost analysis of the scope of work to be
     done.  Once the scope of work cost  analysis has been done,  the Tenant and
     the  Landlord  agree  to  share  the  cost to  build  out the new  suite in
     accordance with the scope of work on a 50% / 50% basis.  The Landlord shall
     pay fifty  percent  (50%) of the build  out cost and the  Tenant  shall pay
     fifty (50%) of the build out cost.  As soon as the  Landlord  receives  the
     check from the Tenant for the Tenant's share of the construction  cost, the
     Landlord shall begin the construction of the new suite.

All Other Terms,  Covenants and  Conditions - Landlord and Tenant agree that the
provisions  of this  RIDER D are hereby  incorporated  into the  original  Lease
Agreement  dated  June 30,  1997,  and  that  all  other  terms,  covenants  and
conditions shall remain the same,  except those terms,  covenants and conditions
that are specifically  defined within this Rider D. The provisions of this Rider
D supersede those in the base Lease Agreement or any earlier Lease Rider that is
associated with the base Lease Agreement.

IN WITNESS WHEREOF,  the parties agree to the terms and conditions of this RIDER
D.

LANDLORD:                                         TENANT:
FORTUNATO DEVELOPMENT, INC.                       NETWORK PERIPHERALS, INC.



By:    /s/ Bernard Fortunato                      By:    /s/ Wilson Cheung
       ---------------------                             -----------------
       Bernard R. Fortunato, PE                          Wilson Cheung
       President                                         Chief Financial Officer

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