You can (if you have a set of reliable backups) is backup your current data, then do a FULL restore including NDS from an old tape where the admin user still exists, then do a partial restore of the old data. This way you'll only lose changes in NDS, but none of your data.
Do you still have a supervisor user? That user should be able to perform most (if not all) admin functions.
Once you get this mess fixed, here is what I recommend you do: What we have done in our company is use the "supervisor" account for network administrators. We have modified the rights of the supervisor account to be admin - with one exception. The "admin" account is actually superior to all the supervisor users in our tree and the password for the account was selected and entered by our company president, then put in a sealed envelope, and then in the bank vault. This allows the network admins to do their job, but the company's board of directors ultimately have full control over everything if some disgruntled employee decides to change all the supervisor passwords. A lot of trust is placed in the network admins, and this gives the company brass the peace of mind that they have full control if they need it. In fact, none of our company brass knows the admin password or the supervisor password. And that prevents people from going in and screwing things up, either purposely or accidentally.
The practice of giving users any supervisor/admin access through their every-day accounts is asking for trouble. Now you know why. The network admins in our company have their own personal account, with the exact same rights as everyone else. When they need to do network admin work, then they use the supervisor account and password, which incidentally is the same throughout the entire company. If somebody were to leave their computer unattended when it was logged in as supervisor, you are inviting disaster!
