Visiontek AGP Radeon HD 2400 Pro Video Card??

I just purchased a new video card and cannot get it to work with my computer correctly. I installed Vista several months ago and my old video card was not compatible. I purchased a new card compatible with my computer and Vista. I uninstalled the old card, installed the new one, and loaded the drivers for the card from the Visiontek website, not ATI because I was told they don't have the correct drivers available. My computer would boot, I would log in to Windows, and then after a minute or two it gives me a black, tan, or other colored screen and I can't do anything. I rebooted other times only to end up getting the blue sreen of death after a few minutes. I formatted the hard drive and reloaded Vista. Then I freshly downloaded the drivers. I still get the same results. I rebooted twice tonight. The first time the screen started flickering on the right side and then I got the blue screen of death. The second time I got a solid black screen and nothing else. I called tech support for VisionTek and they told me I have a defective card, but I am not sure that is right. Any ideas?

My computer is about 3-4 years old. If I disable the video card I have no problems at all!

HELP!!!