The only way to solve it in that case is going directly into the database, but if you have no idea how to do that you should probably get your friend to help.
The tables of interest are mp_Users where the username and password is stored, and mp_Sites.
If the password is encrypted or hashed then you would have to set the passwordformat field back to clear text (0) in the mp_Sites table, then you could edit the Pwd field in mp_Users and type in a new password that you know. Then after getting back in you could optionally change to encrypted or hashed passwords again.
Hope it helps,
Joe