I've been trying to play a couple of games on my pc but they just freeze my computer up and not even task manager can shut the programs down.

For example, i've got Warcraft III (+ Frozen Throne). I've been on a website which tests if your computer can play specific games, and it says my computer passes and that i should be able to play Warcraft III. But when i load it up the monitor turns black which im guessing its setting the screen to whatever resolution or size it needs to be... but then no picture comes up. The sound begins to play but screen remains black, then it crashes. So i bring up task manager, try to close the program then the computer just beeps on any keypresses so have to turn power off at tower. I have a radeon 7000 (think its built in) graphics card and have the most up-to-date drivers for it.

Not sure if it has anything to do with it but Windows media wont play movies either as they begin to play but the computer freezes (like explained above)... the same with winamp and powerdvd. Only quicktime plays clips.