“Unable to load device driver” at boot u

I had to go in the Registry to delete a program,
named Direct Letter Access (DLA) by HP for their
CD Writer + 7200e, that would not uninstall.
Now while booting up, Windows 2000 gave this message:
” Unable to load device driver
\system root\device driver could not be loaded
Error status was 0xc0000020 ”
How can tell what driver Windows wants so I can give it ?
Or could it be related to the old program and how can I stop it ?
Help is much appreciated