Disabled Video Adapter, now no video!

Hello all,

What a mess I got myself into!

When trying to diagnose a software problem, I wanted to eliminate my Display Graphics Adapter as potential cause of the problem. So, in Display Properties, Settings tab, Advanced Button, then Adapter tab, then Properties button, I set the Device Usage pull down menu to "Disable". I then rebooted and the resulting video was overly harsh/bright/with bad refresh rate, as I expected. I then successfully reproduced my original problem, eliminating the adapter that I was originally using as the problem.

Next, I tried to set the adapter back to what it was, and after going to the same area where I disabled it, I THEN DISABLED THE DEFAULT DRIVER THAT IT WAS NOW USING, then rebooted. After seeing the Windows XP bootup screen, with the green "loading" bar moving across, I hear the Win XP "daaaaah, daaaah, daaaaah" sound, and then it goes to a black screen. No video. (In other words, the desktop is not being displayed, but it's there). Then I hear the sound associated with an error message box popping up (but since there's no video, you can't see what it's complaining about, of course).

So I tried getting in in Safe Mode. As the Safe Mode drivers load, it hangs on agpCPQ.sys, which happens to be a video adapter file. Geez! All Safe Mode options behave the same way, hanging up on that file. The Enable VGA Mode, the Last Known Good Configuration mode, and the Directory Service Restore mode are of no help either.

Does anyone know what I should try next?

How long have you waited before deciding that it was hanging? In safe mode it may take a while to load.
You can try to replace the adapter with a different brand, which will force Windowze to re-detect and load the drivers. Or boot with BartPE, load the sytem hive of the registry and delete the info about the adapter in HKLM\System\CurrentControlSet\Display, then unload and save it.
Another choice would be to start with the recovery console and see if you can disable a video adapter related service.

Or go into bios and update nvram or force escd update. Both of these should force a re evaluation of the hardware and windows should reinstall the default adapter.