Check this,
I agree about the windows screen saver / sleep mode settings defenently
check that and also the bios, the other factors involved, i would
recommend this order of checking, try updating the latest drivers for
you motherboard, see if you can format another drive besides that one.
If you can, might be a hard drive problem, next check the power supply
and change that out (you wouldn't believe how many problems are caused
by a crappy PS.) After that it could possibly be a motherboard issue.
After that possibly a cpu issues which is rare but does happen. ( One
of the hardest things to diagnose; if it doesn't fail outright.)