Video Card problems ATI X700

[Izmir]

Hello, I seem to have a somewhat complicated problem with my video card. I normally run WinXP SP2, and for the past year my video card has been running fine, recently I installed Vista on a separate HD for dual-boot, and everything seemed fine for a few days, and today when I turned it off to restart...it just wouldn't.

It will show the boot up screen, and I can enter the BIOS, but it will not go any further than that.

My system specs are as such:
AMD Athlon XP 3200+ (2.2ghz)
1215gb ram
ATI X700 256mb (AGP)
WinXP SP2/Vista Ultimate.

This computer is store bought (an HP), and has many parts swapped out like the power supply (a 500w), etc., and there is some background that may help with narrowing it down. For instance, within the past year and a half, I've had problems restarting it. It wouldn't just straight up restart--instead I have to shut down, and manually turn it on for it to boot up windows. I once narrowed this problem down to my video card, but I never attempted to resolve the issue.

Currently I am running this PC on the onboard video card with no problem on either operating system. I also uninstalled all the ATI drivers and attempted to reinstall the card/drivers fresh, but still stuck at black screen.

I am not sure what the problem might be, and hope someone here can help me out. Sorry if this post is a bit lengthy.