1 ram could be unseated
rare, but ram could be damaged
power supply could be damaged because of power spikes, if you didn't have it plugged in to a surge protector
old power supplies will sometimes spike too, and even damage ram
check for odd processes? CCleaner is good.
sometimes doing a full patch application helps, I use ctupdate to make a update service pack patch dvd, in the process of updating sometimes things get fixed that the windows update dl doesn't fix.
my suggestion is to disable all unnecesary startup processes, ccleaner can help if you don't know how to do it.
then apply ctupdate for your OS
it sounds like software if it isn't your power supply.
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Ours is the age that is proud of machines that think and suspicious of men who try to.
H.M. Jones
They say "Sing while you slave, but I just get bored" - B.Dylan