For about three weeks now my pc has been freezing constantly, most often when I'm playing games or other intensive software. My main suspect was overheating (Which I've had problems with before) but to be safe tried every solution I could think of:
Cleaned case thoroughly
Disable most background tasks from starting up
Removed all USB devices
After all that it eventually just gave up and would no longer even run POST
I then replaced the thermal paste not really expecting anything to work, but it did for a about 2 mins until it froze again, so I was back to the overheating theory but then after restarting I watched the temp from bios where it hovered at about 30 Celsius before it just froze again
So now I'm not even sure that its overheating causing the problem.
What are your COMPLETE system specs? A cheap power supply will cause the sort of problems you describe. Faulty RAM or incorrect RAM settings in the BIOS are also common causes of system freezes. We'll be able to help you better once you post your complete system specs.