When i had installed windows on the other computer i then put it into my new one, it worked :) but... when i tried to run install files for drivers, games etc. it sometimes froze.

I thought ok thats probably normal as it is new, but when i tried to run any game whatsoever it froze on all of them after 30 or 40 seconds into the games. The games ranged from poor graphics like Gunbound and Counterstrike to fairly good ones on Unreal 2003 and Wolfenstein Enemy Terriotory.

I then realised something was wrong, after many restarts and fiddling around a file was lost and i had to reinstall windows :(. I did this again on the other computer as my new one wouldn't cooperate.

Now windows starts and goes into the desktop screen and gives me about 30 seconds to play around then it freezes. All i can do is restart and let it happen again or just turn it off at the wall.

Would this be my power supply? Should i format my harddrive? Would it be overheating? SOMEONE HELP ME PLEASE!!

Then you can be pretty sure that it involves a driver or other program that is loaded. Perhaps this also happens only when you run certain applications. That is another consideration.