to stop my computer freezing?

Some things that can cause computer freezes:
Closed computer case step:
Bad/corrupted drivers, probably the video drivers.
Reinstall your drivers or download the latest from the card's maker and install them.

You'll need to open the computer's case for the followings.
Turn the computer OFF, and unplug it from the wall BEFORE you open the case. Take precautions to ground yourself and always touch some metal part of the case when you work inside.

Bad cooling/overheating
Check the various fans. Remove any dust accumulation with some clean compressed air. (compressed air cans are made for that)

Some component or connection have become loose.

EXTREMELY IMPORTENT TO TURN OFF AND UNPLUG THE COMPUTER!!!!

If you do the following with the computer still plugged you can destroy the component and even the whole motherboard and some other component that you did not manipulate. EVEN with the power off.

Remove and reinsert any extention card. Do the same with the RAM modules. Check the power cable from the power supply to the motherboard and possibly to the video card and make sure they are properly connected.
Check the cables going to the drives.

If none of that correct your problem, you may have a faulty component. (in order of likelyhood)
Try with an alternate video card.
Try swaping your memory. If you have dual channed memory, swap the sticks into the same bank. Swap all the sticks from a bank to another bank. Dual and triple channel sets MUST remain matched together at all times.
Try with another sound card.
Try swaping any extention other card you may have.

If you still have freezes, then it's probably the motherboard that is going out on you: time to get a new computer :(

Kualinar
March 2010