It may be very difficult to completely "install" a VGA driver from DOS, because of registry changes and so forth.
But you can make Windows "forget" or "loose" it's current driver, thus it will prompt you about drivers next time you restart. By deleting the driver files and INF. But that is very risky, because the registry entries will still exist.
The easiest way to do it, and maybe you can't do this, I don't know, is to go into Safe Mode.
In Safe Mode you can delete and erase all the proper files and registry keys.
So give us some background. Can you work in Safe Mode? How come you need to do this?