I'm a Mac OSX user, however run Windows XP (x2) & 2000 with assistance of Parallels which runs them as a virtual OS in a separate window. I keep settings secure between both, only allowing myself to drag & drop files between.

For security for Windows XP, I use: Kapersky firewall & Anti-Virus which comes with Parallels. Anti-virus auto-updates definitions at least once a week sometimes more often, scans the system each time I log-on at least. It tells me of anything suspicious before taking action.

I also use: Malwarebytes' Anti-Malware, Spybot, SpywareBlaster, Ad-Aware, SuperAntiSpyware, Malicious Software Removal Tool. I also use CCleaner regularly to cleanup internet, system & windows explorer temporary files. I only Spybot for spyware on a 2nd Windows XP.