Windows 2000 Keeps Restarting

Hey im running Windows 2k and i have a big question, sometimes when i am using my computer, it will just restart when i try to use an application. it happens usually on the same applications. i tried to run a game the other day but before it got to the game, it jsut restarted, i tried to participate in a gamers survey (where they survey what kind of hardware you have) and my computer just restarted. i dont think its my power supply because im using an ANTEC 430 watts power supply. maybe its my surge protector? im not sure. if anyone can help me please let me know. thanks a lot