I'm having a few problems with my PC, it keeps freezing, nothing works, the mouse cursor doesn't move etc, after i switch the pc off and on again, it takes ages to come back on and when its loaded it runs slow for about 5 mins. it'll probably last about 20 mins or so then it will freeze again.

i did a system restore then a virus scan (nothing showed on the scan), it worked ok for a couple of days, now its started freezing again

any suggestions as to what the problem is? any help is much appreciated.

I'm using windows xp and avast antivirus. it hasn't been updated for a while tho as my subscription has run out.