Device Manager Reports Device Type: Unknown

One of my users called me with a computer problem.  When his computer booted up, the display went black but the computer was still running.  You could ping the computer, connect to remote shares, even connect through remote desktop.

Thinking it must be a hardware problem, I tried other video cards but that didn't change anything.  Using safe mode and remote desktop where the only ways to work on the computer.

Under device manager, the video card was reported as "Unknown" but the driver was installed. Reinstalling and updating the driver didn't help anything.  After hours of crying, I finally find the solution to my problem.  Some registry keys were delete.

To fix the problem, I had to run this registry key file after uninstalling the video drivers.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E968-E325-11CE-BFC1-08002BE10318}]
"Class"="Display"
@="Display adapters"
"Installer32"="Desk.Cpl,DisplayClassInstaller"
"TroubleShooter-0"="hcp://help/tshoot/tsdisp.htm"
"Icon"="-1"

If you don't know how to run this file, copy paste it into notepad.  When you are saving the file, at the save dialog, put a ".key" at the end of the file name and change the "Save as type" to "All Files".  Then double click the saved file.

After updating the registry key, I reinstalled the drivers and everything was back to normal!