K8 notsogrand

I posted a question yesterday about my power supply. (Thanks for reponce)

I'm wondering if I pick up a virus or spyware before the PSU died?
Becouse my PC was acting strange 3 or 4 days before that.
Like;
would not burn dvd,
internet slowed down, infact all programs slow to boot up,
vista would not restart.( had to shut the computer right off)
memery use went from 45-65% to 70-95% With only one program running
vista would boot up then the screen would go black for few seconds. or would
not come on at all.

I ran Norton antivirus and system Mechanic 7 and found nothing.