I had exactly the same problem with my PC running XP about 18 months ago. I also thought it might be heat related, until I proved it wasn't. I tried everything until I finally got totally frustrated and found a permanent cure.

The new PC running Windows 7 is much more stable and is a lot quicker.
Yes, I treated myself to a new one. ;)

Gigabyte were one of the companies worst hit by the capacitor issue
Especially the boards they supplied to Packard Bell. Is yours one of those by any chance?

Gigabyte board was supplied by Scan computer, oop north somewhere, I don't know if it is one of the problem batch. They have not notified me, is there a list of suspicious model numbers/batch numbers/manufacture dates or other means of identifying the bad ones, somewhere I can access?

Rans6......

Not as such

a lot depends on whether they used solid state or wet capacitors

if you look at the board there should be a model number stenciled on in reasonably large writing - something like GA-123xyz