well, im going to take a stab at the 1% then.
by 'hang' do you mean 'freeze'? there is a difference...
if its freezing, then chances are that your overheating.. check all your fans for dust and that they are all working. if it is actually hanging it means there is a programming error or a hardware conflict.
in case you didnt know, a system hang is where the pc doesnt know what to do so it simply stops, it is sometimes responsive, sometimes not.
try reinstalling windows.