You may need to reregister the service. There are batch files created in your iberdir root when you install. One is for registering, and one is for unregistering. Do this:
Run the UNREG batch file and reboot.
Run the REGISTER batch file and reboot.
See if ctlsvr is started when you bring it back up. If not, try to start it again and see if you get a logon failure.
If you get a logon failure, you have to appropriately configure the logon as an administrator user on the machine if you are running win 2000. If there is a user setup, retype the passwords and try again.