Document:

<PAGE>
                                                                   EXHIBIT 10.43

                                 LEASE AMENDMENT

        This document amends that certain Lease Agreement dated November 14,
1996 (the "LEASE"), as amended November 24, 1997, March 17, 1997, March 27,
1998, June 4, 1998, July 21, 1998, November 20, 1998, March 18, 1999, June 3,
1999, October 7, 1999, and March 25, 2000 is made and entered into by and
between DALTEX CENTRE LP, a Delaware limited partnership (the "LANDLORD"),
successor in interest to Blue Lake Partners, Ltd., AND NETWORK ASSOCIATES, INC.,
A DELAWARE CORPORATION, SUCCESSOR IN INTEREST TO MCAFEE SOFTWARE, INC., A
DELAWARE CORPORATION (TENANT), with respect to certain leased premises (the
"PREMISES") consisting of approximately 124,388 square feet of Rentable Area
located at 4099 McEwen, Suites 405, 500, 620, 660, 700, 800, 850, and 4101
McEwen, Suites 100, 270, 300, 506, 545, 550, 700, and 800 Dallas, Texas 75244
(the "BUILDINGS"). (All capitalized terms used herein shall have the same
meaning as in the Lease, unless otherwise specified.)

RECITALS

        Tenant is leasing approximately 124,388 square feet of Rentable Area of
the Building under the Lease, with a scheduled expiration date of February 17,
2003. Tenant desires to expand the Premises by adding the 13465 Midway Building
containing 66,289 rsf. (see Exhibit A), subject to the terms and provisions set
forth hereinafter. The Premises will total 190,677 rentable square feet upon
full occupancy of the 13465 Midway Building.

AGREEMENTS

        For good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, Landlord and Tenant agree as follows:

1.      BASIC LEASE PROVISION NO. 2 "PREMISES". Effective October 1, 2000,
Tenant shall lease the 1st floor (consisting of 14,139 rsf) and 2nd floor
(consisting of 17,455 rsf) of the 13465 Midway Building. The total of these two
floors represents 31,594 rentable square feet. Tenant shall have the right to
expand onto the 3rd and 4th floors (consisting of 17,384 rsf on the 3rd floor
and 17,311 rsf on the 4th floor, hereby referred as "Expansion Floor(s)) anytime
after October 1, 2000 by giving Landlord written notice of the intent to occupy
the Expansion Floor(s). If Tenant exercises such right to expand, Tenant shall
occupy the full floor upon expansion. Regardless of the expansion rights, Tenant
shall expand onto both third and fourth floors by January 1, 2001 and take
occupancy of the entire 13465 Midway Building. Landlord and Tenant shall confirm
in writing the lease commencement date for the third and fourth floors if other
than January 1, 2001. Tenant shall maintain all its then current space at 4099
and 4101 McEwen, however, subject to the termination rights of this Amendment.
Tenant shall have early access rights for construction and occupancy in the
Midway Building beginning August 1, 2000.

2.      BASIC LEASE PROVISION NO. 9 "EXPIRATION DATE". The Lease Term for the
190,677 rentable square feet area shall remain unchanged with an expiration date
of February 17, 2003.

3.      BASIC LEASE PROVISION NO. 3 "BASIC RENT". Effective October 1, 2000, the
monthly Rental Payment shall adjust as follows:

<TABLE>
<CAPTION>
S.F.            DATES:
----            ------
<S>                                                                      <C>
CURRENT MONTHLY BASIC RENT FOR 4099 & 4101 BUILDINGS
124,388         October 1, 2000 thru January 31, 2002                    $193,430.00
                February 1, 2002 thru February 17, 2003                  $198,058.00

INCREMENTAL MONTHLY BASIC RENT FOR THE 13465 MIDWAY BUILDING
14,139          October 1, 2000 through February 17, 2003                $23,565.00
1st floor based upon $20 psf
</TABLE>

                                       1

<PAGE>
<TABLE>
<S>                                                                      <C>
17,455          October 1, 2000 through February 17, 2003                $29,091.67
2nd floor based upon $20 psf

17,384          Upon occupancy through February 17, 2003                 $28,973.33
3rd floor based upon $20 psf

17,311          upon occupancy through February 17, 2003                 $28,851.67
4th floor based upon $20 psf                                             ----------

TOTAL INCREMENTAL MONTHLY BASIC RENT FOR THE 13465 MIDWAY BUILDING      $110,481.67
(UPON FULL OCCUPANCY)
</TABLE>

4.      BASIC LEASE PROVISIONS NO. 4 "TENANT'S PRO RATE SHARE". Effective
February 1, 2000, Tenant's proportionate share of the 4099 McEwen Building shall
be unchanged at 46.16% for all purposes under this Lease. Tenant's proportionate
share of the 4101 McEwen Building shall be amended to 54.09% for all purposes
under this Lease. Notwithstanding, "Tenant's Pro Rata Share", at the option of
Tenant, shall be amended subsequently pursuant to the Reduction Options set
forth in this amendment.

Effective October 1, 2000, Tenant's proportionate share of the 13465 Midway
Building shall be 47.66% for all purposes under this Lease. Tenant's
proportionate share of 13465 Midway Building shall be adjusted at the time of
expansion. Notwithstanding, "Tenant's Pro Rata Share", as of January 1, 2001
will be 100%.

5.      BASIC LEASE PROVISION NO. 5 & 6 "OPERATING EXPENSE STOP". Effective
October 1, 2000, Expense Stop for the 13465 Midway Building shall be set at an
amount equal to the sum of the actual grossed up operating expenses for 2000,
expressed as a function of 66,289 rentable square feet for the 13465 Midway
Building.

6.      BASIC LEASE PROVISION NO. 11 "TENANT'S BROKER". Tenant represents and
warrants that it has dealt with no Broker or Agent in connection with the
execution of this Lease Amendment and Tenant agrees to indemnify and hold
harmless Landlord against all liabilities and costs arising from a breach of
such warranty including without limitation attorney's fees in connection
therewith.

7.      REDUCTION OPTION: During the period of October 1, 2000 to and including
January 31, 2001 and by serving written notice to the Landlord, Tenant shall
have the right to terminate the lease on any of the following suites (see chart
below) and the rent and lease obligations shall be adjusted accordingly. If such
notice is received within the period stipulated herein, the Base Rent and
Tenant's Pro Rata Share shall be adjusted downward based on the rate per square
foot of such space at that time and shall become effective 30 days after
Tenant's notice to Landlord and Tenant's vacating such suite(s). Additionally,
an amendment shall be submitted to Tenant, which addresses the economic terms of
the Lease affected in the vacating of the suite(s) and the termination of same.
Failure of Tenant to submit notice within the period shall be deemed an
acceptance by Tenant of such space for the remainder of the Lease Term.

<TABLE>
<CAPTION>
 BUILDING       SUITE         RSF     ANNUAL BASIC RENT/SF  MONTHLY BASIC RENT
 --------       -----         ---     --------------------  ------------------
<S>             <C>           <C>     <C>                   <C>
 4099           405           2,123          $18.25              $3228.73
 4099           620           5,983          $17.25              $8600.56
 4099           660           1,775          $20.00              $2958.33
 4101           100           3,843          $20.00              $6405.11
 4101           270           3,663          $19.00              $5799.00
</TABLE>

8.      EXHIBIT "D". Work Letter Plans Agreed Upon/Finish Allowance, paragraph
2.1, shall be amended as follows: (1) Landlord shall provide an allowance up to
Two Hundred Twelve Thousand Five Hundred Dollars ($212,500) for the 13465 Midway
Building (The "Finish Allowance"); (2) Tenant shall be responsible for the
balance of the costs for the leasehold improvements, as well as the management
of the design and construction of the leasehold improvement, subject to
landlord's approval of the Approved Plans; and (3) Landlord's "Construction
Management Fee" of five (5%) of the construction Contract Sum shall be deleted.

                                       2

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9.      FORCE AND BINDING EFFECT; GOVERNING LAW. Except as modified hereby and
by the Amendments to Lease Agreement, all other terms and conditions of the
Lease shall remain in full force and effect and this Amendment shall continue to
be binding upon Landlord and Tenant and their respective successors and assigns.
The Lease and this Amendment shall be governed by Texas law.

10.     RENEWAL OPTION. This expansion space (13465 Midway) shall be subject to
the same renewal option terms as specified in the Lease. Tenant shall, however,
have the right to renew the leased space in each building independently from the
other buildings (e.g., Tenant shall have the right to renew the 13465 Midway
Building without renewing the spaces within the 4099 McEwen Building and/or 4101
McEwen Building).

11.     SIGNAGE. Tenant shall have the right to place a company sign on the
13465 Midway Building and the 4101 McEwen Building, subject to the current
signage criteria used for signage on the 4101 McEwen Building. Tenant agrees to
rescind its signage rights for the 4099 McEwen Building in return for the
signage right herein stated.

12.     RIGHT TO TRENCH BETWEEN 4101 MCEWEN AND 13465 MIDWAY BUILDINGS. Landlord
shall grant Tenant (at Tenant's sole cost) the right to trench between the two
buildings for telecommunication/data purposes. Tenant agrees to perform such
work in a professional manner, observing all required permits. Landlord
maintains the right to approve all work. Tenant will be required to repair such
work to its original condition.

13.     DELIVERY OF THE 13465 MIDWAY BUILDING. The Midway Building shall be
delivered to Tenant free of prior tenancy, debris, and/or personal property
(except for those furniture and fixtures as which have been purchased by Tenant
from the prior tenant). If the Midway Building is not delivered by August 1,
2000, Tenant shall be credited one month free rent for every month (or prorata
thereto) that Tenant is delayed full and complete access into the Midway
Building.

14.     EXISTING LEASEHOLD IMPROVEMENTS AND FIXTURES. All existing leasehold
improvements and fixtures shall remain in or around the 13465 Midway Building,
including, but not limited to the UPS, one generator, security system, and all
existing infrastructure systems in the data center, etc.

15.     RIGHT OF FIRST REFUSAL: Notwithstanding herein to the contrary, Tenant
shall, subject to prior rights within the 4100 Alpha Building and the 4100
McEwen Building in The Centre complex, have a continuous Right of First Refusal
to lease any available space or contiguous spaces in excess of four thousand
(4000) square feet in the 4100 Alpha Building or the 4100 McEwen Building during
the term of this Lease. Tenant shall respond in writing to Landlord within five
(5) business days after receipt of Landlord's written notice of any prospective
lease in the 4100 Alpha Building or the 4100 McEwen Building. Absent of any
response from Tenant or if Tenant decides not to exercise such right for the
prospective lease, Landlord shall be free to lease such space to any other
party.

                                       3

<PAGE>
Executed on this 31st day of July 2000.

LANDLORD:                DALTEX CENTRE LP, a Delaware limited partnership,
                         successor in interest to Blue Lake Partners, Ltd.

                         BY: DALTEX CENTRE GP, INC.

                         BY:   /s/ RON CHERRY
                            --------------------------------
                         Name:  Ron Cherry
                         Title: Vice President

                         BY:   /s/ YVON TESSIER
                            --------------------------------
                         Name:  Yvon Tessier
                         Title: President

TENANT:                  NETWORK ASSOCIATES, INC.
                         (A DELAWARE CORPORATION)

                         BY:   /s/ PRABHAT K. GOYAL
                            --------------------------------
                         Name:  Prabhat K. Goyal
                         Title: CFO

                                       4

<PAGE>
                                   EXHIBIT "A"
                           (SEE ATTACHED FLOOR PLANS)

                                   [GRAPHIC]

                                       5<PAGE>
                                                                   EXHIBIT 10.44

                       AMENDMENT NO. 12 TO LEASE AGREEMENT

        This Amendment No. 12 to Lease Agreement ("Twelfth Amendment") is made
and entered into this 24th day of January, 2001, by and between DALTEX CENTRE
LP, a Delaware limited partnership ("Landlord"), and NETWORK ASSOCIATES, INC., a
Delaware corporation, ("Tenant").

        WHEREAS, the predecessors of Landlord and Tenant entered into that
certain Standard Office Lease Agreement ("Lease"), dated November 14, 1996, as
amended on March 17, 1997, November 24, 1997, March 27, 1998, June 4, 1998, July
21, 1998, November 20, 1998, March 18, 1999, June 3, 1999, October 7, 1999,
March 25, 2000, and July 31, 2000, covering, in the aggregate as of January 1,
2001, approximately 190,677 rentable square feet of space ("Premises") in
buildings (the "Buildings") located at (i) 4099 McEwen, (ii) 4101 McEwen, and
(iii) 13465 Midway Road ("13465 Midway"), in Farmers Branch, Texas 75244; and

        WHEREAS, on July 31, 2000, Tenant and Landlord entered into that certain
Lease Amendment whereby Tenant expanded its Premises into the Building commonly
known as "13465 Midway", and pursuant to Section 14 of such Lease Amendment,
part of the equipment which Tenant leased thereunder included two existing
emergency back-up generators (the "Generators") located in an enclosure outside
of the Building at 13465 Midway, and as a consequence thereof, Tenant now
desires to clarify its rights and duties with regard to the Generators and the
portion of the Premises wherein such Generators are located; and

        NOW, THEREFORE, for and in consideration of the mutual covenants
contained herein, and other good and valuable consideration, Landlord and Tenant
hereby further amend the Lease, as follows:

        1.      GENERATORS; MODIFICATION OF ENCLOSURE WALLS

        As part of Tenant's expansion into 13465 Midway, Tenant acquired from
the previous tenant of such leased space two emergency back-up generators
located in a separate exterior enclosure/structure (the "Generator Enclosure")
located adjacent to the Building commonly known as 13465 Midway. As part of
Tenant's construction of the leasehold improvements to 13465 Midway, Tenant will
(i) install one additional Generator in the Generator Enclosure, and (ii)
construct certain modifications (the "Modifications") to the existing enclosure
walls to the Generator Enclosure wherein the original Generators were located in
order to accommodate the new, additional Generator. The Modifications to be made
by Tenant to the Generator Enclosure shall conform to the plans and
specifications therefor attached hereto as Exhibit B, which plans and
specifications have been approved by Landlord. In constructing the
Modifications, Tenant must comply with all governmental laws, rules and
regulations applicable thereto. Landlord's approval of the plans and
specifications for the Modifications shall not be construed as any indication
that such plans and specifications comply with applicable laws, such compliance
requirement being solely the responsibility of Tenant. The Generators (which
shall be defined to include all associated

                                      -1-
<PAGE>
equipment, including fuel tanks and piping, wiring and circuit breaker panels)
will be located only in the locations specified in the attached Exhibit A, and
none of such Generators shall be relocated from such locations without first
obtaining the written consent of Landlord, which consent shall not be
unreasonably withheld or delayed. At all times during the term of the Lease,
Tenant shall be regarded as the owner of the Generators.

        2.      MAINTENANCE OF GENERATORS AND GENERATOR ENCLOSURE

        Throughout the Lease Term, Tenant will responsible for maintaining and
repairing the Generators and Landlord will be responsible for maintaining and
repairing the walls and exterior structural elements of the Generator Enclosure,
and that portion of the Generator Enclosure where the Generators are located in
the same manner as specified in Section 6.1 of the Lease. Landlord shall have no
obligation whatsoever to maintain, repair or replace any portion of the
Generators. Tenant shall not be responsible for or obligated to maintain, repair
or replace that certain generator (and associated equipment) located within the
Generator Enclosure, which generator is owned and operated by another tenant in
The Centre office complex. In the event that Tenant shall elect to replace any
of the Generators, Tenant shall be solely responsible for the cost and
obligation to do so. Any alterations to the Generator Enclosure must be first
approved by Landlord.

        3.      INSURANCE

        In addition to the insurance required to be maintained by Tenant under
Section 7.201 of the Lease, Tenant shall also be required to obtain and
maintain, throughout the Lease Term, environmental insurance on the Generators
(including that portion of the Generator Enclosure where the Generators are
located) in such amounts and specific types of coverage and endorsements as
Landlord shall reasonably specify and require. In that regard, Tenant will name
Landlord and the manager of 13465 Midway as additional insureds under such
environmental insurance coverage, and Tenant will provide to Landlord a
certificate of insurance, in form and substance acceptable to Landlord,
indicating such coverage and additional insured endorsement for Landlord and the
property manager of 13465 Midway.

        4.      GENERATOR ENCLOSURE PART OF COMMON AREAS

        Hereafter all elements of the Generator Enclosure, and that portion of
the Generator Enclosure where the Generators are located are part of the Common
Areas for all purposes under the Lease; and therefore, all duties and
obligations of the Landlord and the Tenant under the Lease applicable to the
Common Areas will hereafter be likewise applicable to such Generator Enclosure.

        5.      GENERATORS ACCEPTED "AS-IS"

        Tenant hereby accepts the Generators and that portion of the Premises in
which the Generator Enclosure is located in its "as-is" condition, except for
latent defects, and no improvements or alterations to the Generators shall be
required by Landlord.

                                      -2-
<PAGE>
        6.      RATIFICATION

        Except as amended hereby and by the previous amendments to the Lease,
the Lease shall remain unmodified and in full force and effect.

        IN WITNESS WHEREOF, Landlord and Tenant have caused this Twelfth
Amendment to be executed on the date first written hereinabove.

TENANT:                                  LANDLORD:

NETWORK ASSOCIATES, INC.,                DALTEX CENTRE LP,
a Delaware corporation                   a Delaware limited partnership

By: /s/ WALLACE HONG                     By: Daltex Centre (GP) LLC,
   ------------------------------        a Delaware limited liability company,
   Name: Wallace Hong                    general partner
   Title: Vice President
          Corp Real Estate
                                         By: /s/ RON CHERRY
                                            -----------------------------
                                            Name: Ron Cherry
                                            Title: V.P.

                                         By: /s/ JEAN FRANCOIS FOURNIER
                                            -----------------------------
                                            Name:  Jean Francois Fournier
                                            Title:  V.P.

                                      -3-
<PAGE>
                                    EXHIBIT A

                             LOCATIONS OF GENERATORS

                                   [GRAPHIC]

                                      -4-

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