Urgent help. Windows 2000 SP4 problem.

The primary Domain Controller is messed up with SP4.

I cannot loadup windows 2000 server normally. There is an
error box complaining "At least one driver fail to
register...". After a while it stuck at "preparing
network connection" and seems totally dead.

I tried to boot into "Active Directory Restore Mode". It
actually passed the "preparing network connection" screen
but I cannot login using my current Administrator
password.

I tried to boot into "safe mode with networking". It also
stuck at "preparing network connection" screen.

I am wondering how I bring the PDC back to normal and if
there is a need, how I can rollback. I chose "achiving
file" when I did installation. Is that mean I can
rollback?

Frank