Power problems can be caused be a few things. I would run through this list...
Check to make sure all vents are free of dust.
Check that your processor fan - power supply fan - case fans are free and clear of dust and they turn freely. Additionally, pay close attention to the processor area - no dust allowed!
Check to make sure everything
is seated firmly. Reseat memory - adapters that are in your system. Make sure all cables are plugged and snug - inside and out.
Check to make sure your power switch is firmly attached to the case. Some models have plastic tabs holding them in place.
Check to see if your power supply's voltage selector is on the right setting. 115 vrs 230
Try another power source. If you have a surge protector, it may have been hit, and become unstable. Try another house receptacle.
and test your memory. It creates a boot disk and has easy to follow instructions.
Run diagnostics on you hard drive. You can use our Hard Drive Installation and Diagnostic Tools
and run it. It will give you temperatures and detected speeds of you fans and system. It will also display the voltages your power supply is outputting.
If all of the above checks out ok, unplug hard drives, floppies, CD/DVD drives and power the computer. If it runs fine then, Start to plug components back in.
Finally, replaced the power supply. They go bad.
Good luck rnuckols. I hope this helps.