[Beavis68]

I have read pretty good things about Norton 2007. Does it contain a firewall?

Turning off Windows defender sounds like a good place to start like erbby said

Many times Virus software doesn't uninstall completely. If you only have the firewall version of ZA it will not slow your system down.

Also, set Norton so it doesn't scan your system at startup and doesn't scan files everytime you open them. Scan anything new that is suspicious and scan your system once a week or so and you should be in good shape.