Computer issues with high quality games

I have a great computer with alot of space on it and a lot of great upgrades for gaming... but its always freezing/locking up during games like battlefielld 2/2142 and spider man movie and basically any high quality games (I meet all the requirements and more) and by lock up i mean the game freezes and the current sound loops the only way out is to restart the computer with the button on the tower. Its not overheating (old issue fixed and done with) But me and my father think its our 430W power supply not being able to keep up, or else our 1 GB of RAM. Any ideas on how to fix this? Our budgets tight and i dont feel like spending anymore money on something that wont help.

This will probably turn into a hardware thread so you may want to go to the hardware forum and start another thread since this one will more-than-likely get locked or moved. If you write another make sure you put in your full system specs, can't really judge a problem without knowing what is in your system.