nVIDIA eGeForce 6200 freezes cpu

I have an nVIDIA GeForce 6200 graphic card and I am a very big fan of videogames, I used to play them, but suddenly the graphics became chopped, showing triangles and the characters were choped, and when I start a game the computer freezes and I have to restart the cpu, any1 has the same problem??, can any1 help me fix the problem??, any1 knows what the problem is??

I have send the same quesiton to the nVIDIA suport page and they couldnt solve my problem, so I hope any1 here can solve it

My system specifications:

Intel Pentium 4 2.54 GHz
Windows XP uE sp2
Memory 768 RAM
VGA nVIDIA GeForce 6200 256 megas
Direct X 9.0c
Power supply: 300 watts

and get a new 450w psu. for the ati 2600 serie you'll need more than 300