After reset, Windows 7 will become unresponsive

Last weekend I reset my Gateway FX6840-03e that I’ve had for over three years, to its original factory settings just as a hard drive/housekeeping measure. The reset went fine, but a few days later I’m now experiencing a problem where it will become completely unresponsive after it is on for a certain period of time, like less than two hours. Nothing on the desktop will respond. CNTL+ALT+DEL will not show up, and neither CNTL+SHIFT+ESC. Absolutely nothing. I’ll just get the cursor spinning circle response if I click on anything. Does anyone have any ideas in how to fix this so I can avoid resetting the factory settings again and have to download over 200 Windows updates? I’m running Windows 7 x64 SP1 with the latest updates.