If the system defaults to VGA mode (or only boots to the VGA selection), use Regedt32 to navigate to:
The \Device\Video0 value name contains a registry key that has the video driver that is configured to load.
If you navigate to that key, KKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\<videodriver>\Device0 for example, the data value in InstalledDisplayDrivers contains the name of the video driver that was loaded. If this points to another registry entry, some third party software, may have altered it (PcAnywhere may have set it to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\AW_HOST\Video0).
Verify that the driver file, <videodriver>.DLL, exists in the %SystemRoot%\System32 folder and that <videodriver>.SYS exists in the %SystemRoot%\System32\Drivers folder. If these links and/or values are not correct, resolve the problem so the system starts correctly.
If the links and values are correct, and the driver files are in their proper folders, verify that you have the latest driver for your card.
Here is a sample of what the above entries might look like when using an STB Velocity 128 video adapter:
The Device\Video0 value at HKEY_LOCAL_MACHINE\hardware\DeviceMap\Video contains:
This entry has an InstalledDisplayDrivers value that contains stbv128.
See the following for additional video issues:
Q162577 - STOP: C0000143 MISSING DISPLAY_DRIVER.DLL.
Q154754 - STB PowerGraph Video VLB Display Adapter Not Detected.
Q155681 - Troubleshooting Display Problems in Windows NT 4.0.
Q174567 - AGP Video Support for Windows NT 3.51 and 4.0.