Video Card Help

My onboard nvidia nforce 4 video works fine, but when I plug in my His HD4670 turbo, it can't get past the bios screen without the whole screen getting wierd colors and things on it. Is my video card's VRAM DEAD?

I'm sorry if my post sounded mean. I've got a biostar mcp6p-m2 v.6.x mobo am2. It's 1st gen pci e but the card's 2.0. I've had it since may. 4 months is not an expected video card life I would think. So, anyways..

When I turn on my computer with the onboard port, everythings A ok.

When I turn it on with my HIS HD4670, everythings fine for a few seconds, or up to 5 minutes, but then the whole screen becomes corrupted. Sometimes I don't make it past post....

I noticed that my new case was covering its exhaust.... My uncle looked over the board and said there's a few burns here and there, but, if it was burnt out wouldn't it not work at all..

?

Anyways, thanks for replies, and I really hope for help.

Burn spots on semi conductors,,means that they are not up to scratch,,and may not be able to output the signal/waveform that they were designed to do,can cause alteration of systems resistance reduce current at critical places,remember we are dealing with micro voltages here it does not take a lot to snafu ,need to try part[s] in other box to ascertain functionality..