windows xp lockups

i know this may belong in the software section, but i suspect it may be a hardware issue.

my specs
amd athlon xp 3200+
nf72 abit mobo
2 g ram
ato x800 pro
psu 450 or 500 w not sure

ive ran panda scan, avg scan, spybot scan. cpu is 32 degrees as it mobo. auxillary is 30 (i just reaseted my cpu with thermal compound and dust blasted every crevice the inside of my pc has).

my problem. basically my computer locks up. the mouse moves around, i click on stuff, nothing happens. then about a minute later everything kicks in and the pc wakes up. at startup it (the deep sleep) can last 5 mins. this only started happening yesterday. oh fellow geeks what ever could the problem be?