Video card just stopped working

My system is a Dual boot XP Pro SP3 and Vista Ultimate SP1. Intel 965
chipset, E6700 CPU, 2GB RAM, Lightscribe DVD-RW, with multiple hard drives
and multiple partitions. I was running a Geforce 6600GT 128M PCIe video card.

Last week I was working in XP, and when I booted back to Vista, the monitor
reports no signal. It gives me the boot up screen with the scrolling bar,
then goes black when the GUI starts to load. I can hear the boot sounds, I
know it is running, but no video signal. I shut it down and booted into XP,
where it worked fine. I went back into Vista, safe mode and disabled the
video card, now it booots up and runs. I contacted Nvidia, who had me update
drivers, and then try several older drivers, but the problem still exists. I
put in a new video card, a Geforce 8600GT 1GB PCIe, but the problem is the
same. Through all of this the system boots and runs fine in XP, and it runs
OK in Vista using the standard VGA driver (just no hardware acceleration, and
no Aero).

During this process I found out that dual booting with XP deletes all of the
previous restore points, so I can't go back. I did try uninstalling all of
the recent updates on the system, and then reapplying the drivers, but still
no help.

I really don't want to have to reload Vista...AGAIN...Any suggestions?