What I have learned recently is that anytime an os is vunerable to virus attacks,worm invasions,or trojan timebombs,the user MUST run anti-virus software continuously and it doesnt matter if its the best anti-virus in the universe what ultimately happens is symptomatic of what you are experiencing.And that is due to anti-virus and malware programs running it affects most everything else on a computer.Slow running sluggish response can be traced back to anti-virus programs due to the program itself if not continuosly updated and reconfigured will read new code in vista as a threat and while not shutting down system entirely it will wrek havoc in other areas in terms of functionality of programs and actions on your computer.Switch to an imac youll be glad you did as i have.