I've lived with this for years, but I'm getting tired waiting for a new PC.

My PC restarts itself.
Unpredictably, in Windows Explorer, if I'm doing alot of file manipulations, going into directories, coming out, expanding directories in tree view, moving directories with drag & drop into other directories, if I do this often enough, "BAMF!", My PC restarts.

In Internet explorer, Clicking threads in Forums, reading, back buttoning out, click the next link, read, Backing out, etc... etc..., "BAMF!", My PC Restarts.

It might not happen for weeks at a time...
It Might happen 5 or more times in a day {Especially if I'm at the USA Message board for "The Dead Zone" }...

Needless to say, I'm now pretty good at saving code after writing 10 or more new lines...

Any Speculation as to how to fix this irritant?
Outside of a New PC, anyways.