Anilrgowda

Re. the Security Center reporting that AV is not installed, I think this is just a communication problem between McAfee and the Security Center. Just select the option in Security Center that you will monitor the AV yourself, and it should not complain any more.

Re. the Windows Defender not being recognized correvtly, you can fix it as follows, in fact this may fix the mcAfee problem as well:
(you can find Command Prompt in Start -> Programs -> Accessories)
(It is probably also a good idea to create a System Restore point before starting, which you can do with Control Panel -> System -> System Protection -> Create)
----------------
Right-click Command Prompt and Run as Administrator. Type the following
command:

winmgmt /verifyrepository

If the system returns "WMI repository is not consistent", run this command:

winmgmt /salvagerepository

The first time you run this it will fail. (It will issue stop commands to
the services causing it to fail. It might take a couple minutes for the
services to shut down). Run the command again. You actually may have to
run it 3 times before it finally runs and completes on its own.

Reboot your system.
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The above is from Security Center says that Windows Defender is turned off - Vista Security

Let me know if this fixes it. Thanks.

Anilrgowda

Have a look at
Access Runtime Workaround on XP SP2 - MSKB 837150


Good Luck!