Power supply dying?

My computer, every few days, randomly restarts. I'm never there when it happens, but when I go to use my PC sometimes, I turn on the monitor and found that it restarted?!

Is my power supply dying? I have no spare PSU to switch in, so I can't test it that way. Is there any way to figure out if my PSU is having problems/dying?

Please help!!

-- Twist

Restarts can be caused by heat sensitive components, overclocking, and corrupted software. If you are overclocked, back off to defaults. Check your temps. See if your cpu (higher than mid 50's C) or video card (depends on the card) are running too hot.

You can reload your operating system to clean out corrupted files.

I have never overclocked this PC (its not really possible, Intel mobo). I don't think I have any corrupted files, but I'm gonna run Scandisk and Defrag later to check.