|And again ....|
GET YOURSELF A WINTERNAL BOOT CD
BOOT FROM CD and check if it's hardware.
Since when is it doing this??
What is the last thing you changed (of the other person)
If they they say I HAVE DONE NOTHING ask them who else could have done something and if so what else could that other person have been doing, SO THEY DON'T NEED TO EMBARRASS THEMSELF ;-)