Posted 29 July 2006 - 04:03 PM
And it might be that the computer is not shutting down but the videocard is overheating. If you have a separate video card (not built onto the motherboard) it may have a built-in fan that has quit. If so, it may be necessary to replace it because they often suffer heat damage and will fail even if you can obtain a new fan. And as already suggested, try a different monitor.
Oh, and check your power settings - make sure that they aren't set to shut down anything. Just set everything to "never." Right-click your desktop, choose Properties, then the Screen Saver tab, then the Power button.