I was all set to give you advice on how to reset your administrative password on a Mac OS X system when I realized with a bit of a sinking feeling that you're on the older OS and that I no longer have any computers that are still running MacOS 9.
Instead, I tried digging around online to find some troubleshooting help for the older OS, starting with Apple's support knowledgebase.
One match that might help you find your answer is Setup and Management of Multiple Users on MacOS 9, which talks about the Multiple Users control panel. But that's not exactly what you seek, because you won't be able to use this if you're not the administrator.
The next possibility? Reinstalling MacOS 9, though that's obviously not the first choice.
Hmm... digging back in my memory: what happens when you reboot the computer? Don't you automatically get logged in as the administrative user anyway? If not, what would happen if you rebooted off a utilities disk like Norton Utilities? I think I'm still mired in the world of Mac OS X and its much more sophisticated user model, but MacOS 9 can't really have you shut out, as I recall.
So that's what I'd try. If it doesn't solve the problem, please detail exactly what does happen when you restart the system.
Good luck!
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I used to use this method:
Boot from a CD or other bootable disk.
Go to System Folder > Preferences folder.
Delete the Multiple Users preferences file.
Reboot.
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