User recovery help.

Hi all.

I have been given a laptop to try and sort out. For some unknowen reason the user account has changed from an administrator to a guest account.

Tried logging on through safe mode but nobody knew the administrator password. I cleared the password and gained access to the system via safe mode. When trying to access the system via admin normaly the admin account was not activated.

So safe mode again and reactivated it finally got into the system in normal mode but now the user that was guest that i want to make admin again con not be found. If i go looking in the users folder there user name and folder is there.

If i try to create a new user with the same user name the system will not let me. I need to get it back. Any ideas on how to achieve this?