Please see my post above, but a new development is that I opened up the display driver in device manager. It showed two ATI Radeons, one that was supposedly funcitoning, and one that was not. When I left the device manager, it told me I would need to save my changes and reboot... which I did, though I don't recall changing anything. It went to bluescreen during the reboot with a STOP for ati2mtag.sys Page_fault_in_nonpaged_area. Tried rebooting again and got the same error. Then I rebooted in Last working configuration, which got me back into windows, and I'm still getting the New Hardware Found... PCI device issue.
Earlier today, when I originally installed the drivers for the card, I used the manufactuers disk, but it kept failing and giving me the c000021a fatal system error. Finally I booted with the XP disk in and it got me back into my system without the error, at which point I downloaded the latest drivers for my card (from July of this year... it's listed in the post above). But now I'm wondering if I have multiple driver installs or something.
I'm seriously starting to lose my mind here.