First thing i would do from the information you gave would be to get a can of air or 2 and go to town cleaning all of the fans and power supplys. Athlon chip set run hotter than heck and it you have poor ventilation it would do simular thing to the examples you mentioned. After that i would do like swamp said except then i would do a THOROUGH scan disk on them. lots of people miss this part and it pretty important. It finds all though little worn out bad spots on the drive. It could be the drive you use for your boot drive is to small and lacks serroius space.