Thanks for posting.
Just to make sure we're on the same page: Do you already know the username/password and just want to change it or do you want to reset it b/c you do not have the password?
If it is the former, you can go to the Admin Console > General Settings > Admin Console tab > Change User Name/Password button.
If it is the latter, unfortunately there is not a setting to automatically clear the username/password and reset it. You will not, however, have to un/re-install the software to wipe the slate clean.
If you choose to do so, try the following:
1. Close out all of the databases
2. Close the Admin Console
3. Go to FileMaker Server > Admin > Conf. Delete the .xml files in this Conf folder.
Now, when you launch the Admin Console it will act as if it Deploying for the first time and you can enter the proper configuration information including username/password.
This avoids the steps of un/re-installing the software, but if you prefer to you can do so.
Hope this helps.
Thanks a lot.This did indeed the trick.
I deleted the xml files, rebooted the server and I was able to set a new login and password.