NT Database is Locked

NT 4.0 with SP 6a

After I added RAS services and PPTP protocol,
when I tried to look it PPTP’s property, it took forever. I reboot the server and tried to removed PPTP and reinstall again. I got
an error: “Database is locked, please try it
later.”

I don’t know what happen. I still could not add or remove services.

Any help would be appreciated