Reboot with the menu (use F8 if necessary), and choose option 6 (Prompt only). Change to the main windows directory, unprotect these files, and make these copies:
cd \windows (or wherever) attrib -r -s -h system.* attrib -r -s -h user.* copy system.da0 system.dat copy user.da0 user.datReboot. This should use the last good registry settings.
Registry settings
If you have the problem that the registry settings say to use a particular .VXD file, and the above has not worked, then you could try this.
Boot in safe mode, open a dos box (ignore the warning), and type "regedit".
This should bring up a not well publicised program that allows you to edit
the registry settings. In my case, I found the required setting under
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VXD
