Here is a filemaker article on resetting the server admin console password.
In short, you can only reset the password if you know the 4 digit pin (as set during install) and the account name. The pin is often the school center code or the postcode, and the account is often Admin or Administrator.
If either of the above is not known, then the only way to reset is to reinstall Filemaker Server on that machine. Please contact us if you need more detail.
