I've recently started having issues where my PC will switch itself off when I run a number of programs or just a demanding one, like a game. It's not a heating issue, Speedfan's indicating all my hardware is at or below 60'C.

This has been a tolerable issue until today; where after starting my PC up after the PC had switched itself off. I could no longer see the desktop - no icons, no taskbar, nothing. I could, however, load up safe mode, and I used that to look up this issue. I found that people who've had this issue before could in fact ctrl alt delete when they're looking at this before mentioned black screen, whereas I cannot. I can't do anything, and there's no hard drive activity. I solved that particular problem by starting up in safe mode and using system restore, however, as expected, this did not fix the shutting down under stress issue.

I have a feeling this shutting down under stress might be on account of my slightly overclocked CPU. I'm running a Q6600 with a stock speed of 2.4GHz, but I've bumped it up to 2.9GHz. Although it's been this way for the better part of a year and I've had no issues, it's a good place to start, so I'll be clocking that back down to 2.4GHz sharpish. Also, I'm running mixed RAM. I know, I know, it's a big no-no, but there's nothing I can do about it right now though.

Anyway, I'd really appreciate if someone could shed some light onto what they think this issue might be, and maybe a possible solution. I'm running a 32 bit version of Vista SP2.

Originally Posted by richc46

Welcome
The problem could very well be the result of your overclocking, but lets not go there yet.
Sounds like a memory problem, take memtest
Guide to using Memtest86+ - Geeks to Go Forums
If that does not show anything try a clean boot to diagnose.
Troubleshoot Application Conflicts by Performing a Clean Startup - Windows 7 Forums
If all is negtative
Run a full anti virus scan
Download and run a full scan with malwarebytes. Makes sure to update before the scans.

Thanks very much! I'll start working through those steps tomorrow afternoon when I get home and I'll let you know how I get on.