>Thanks Hilmar, but I failed to mention that the OS is NT4. When the system boots, I never see an option to boot in VGA mode.

In NT4 you should get a boot menu (including a VGA boot mode), by default, that hangs around for 30 seconds. Some people don't like to wait that long, so they edit their BOOT.INI file and reduce the TIMEOUT value, and/or they remove "redundant" OS options from its boot menu. If someone has reduced the timeout to zero, or removed the other boot options it could account for what you're seeing. ( http://www.winguides.com/registry/display.php/243/ )

Just in case timeout has been set to 1, try holding down the down arrow key while NT starts to load - it might cause the menu to stop and let you pick the VGA option.

If timeout has been set to zero, or all the other boot options have been removed you're in a bit of a bind. I can't recall offhand if NT4 supports FAT/FAT32 system partitions; if so, and yours is still FAT, you could create a Windows 98 boot disk, include a DOS text editor, boot to the Windows 98 command prompt and edit the BOOT.INI file (it's SYSTEM and HIDDEN).

Sample BOOT.INI file: http://www.microsoft.com/technet/prodtechnol/winntas/tips/techrep/boot.mspx

* Before doing ANY of the following I'd recommend you have a good backup *

If it's NTFS you need to boot something that can mount an NTFS volume. Though I haven't tried any, some appear to be available e.g. http://www.ntfs.com/boot-disk.htm
* UPDATE * the above product can't write to the NTFS volume, it's read-only. You might have better luck with something like this: http://www.winternals.com/products/repairandrecovery/erdcommander2002.asp?pid=erd

I believe some people are starting to use bootable CD-ROMs containing the Knoppix distribution of Linux for troubleshooting of this sort. It might be a bit of a hassle finding the right download and configuring it for your system, though.
http://www.knoppix.net/forum/viewtopic.php?t=11736
http://www.shockfamily.net/cedric/knoppix/
http://www.troubleshooters.com/linux/knoppix/knoppix_rescue.htm

Yet another idea, if you have another NT4 system, would be to temporarily attach the hard drive to the other system as a slave or secondary drive. When NT4 boots on the other system, it should automatically mount the NTFS volume on the problem drive as a new local drive, allowing you to view and edit the BOOT.INI file. You *MIGHT* also be able to do this on a W2K or XP box, but I'd be a little leery of doing that because their versions of NTFS are slightly different from NT4's. It's possible the newer versions of Windows might "mark" the volume and it might no longer be NT4 compatible.