Where is the password stored when there is no location given? In case a HDD is formatted, which file is to backed up so the database can still be opened after the format?
The password is not stored, it is required to decrypt the database.
The only file you need to backup is the database, e.g. database.kbd.
If you are locking your database using a key-disk (you select a drive in the combo-box of the password dialog), you also need to backup the file "pwsafe.key" in the root directory of the drive you selected.