My screen gets distorted with random rainbow colors

[SystemDown]

So i built a pc and it still has no new video card so i used my old inno 3D 9500 gt. So everything is fine at first but after a few minutes of gameplay my screen gets distorted with different colors, i can't see anything just random color lines and eventually the pc stops responding so i have to restart it. i tried again and it happens again, so i try playing low end games likes Warcraft 3, battle realms and other games that doesn't putt any stress on the video card but it still happens. I changed the thermal paste and checked if the fan is working so what should i do??? please help. I currently have no cash to buy a new high end video card so i have to stay with this one for a few weeks

My computers specs:
Intel Core i3 3220 3.3ghz
MSI H61M-P31 H61
RipJaws 8gb 1333 (10666CL9D) 2x4
500gb Seagate Barracuda 7200rpm
250gb Seagate Barracuda 7200rpm

 

[warhead0]

When you say you changed the thermal paste, was that on the CPU or GPU?

Are your drivers up to date?

Perhaps try cleaning the GPU of all the dust you can see.

Another possibility is that the GPU is beginning to fail. Are you able to try another GPU?

 

[SystemDown]

I changed the thermal paste on the gpu and cleaned it thoroughly, i just downloaded the latest drivers from nvidia. Maybe the GPU is failing but i hope not because i still haven't bought a new video card

 

[shardey]

Monitor you GPU temps while putting it under stress. It may be getting too hot.