If you forgot your master password you can no longer open your database. Due to the AES 256-bit encryption of all Password Depot databases it is technically impossible to open the file without entering the correct master password. Even AceBIT cannot help you in this case since we do not store any data of our customers and there is no option to restore a master password.
You can only try to enter different master passwords in order to guess the correct password. In any case, this will not lock your database.
HINT: If you forgot your master password this does not mean that you cannot use Password Depot any longer or that you have to re-install it.
The full version of Password Depot allows you to create an unlimited number of databases. If you no longer remember the master password of your current database, launch the program and go to the Database Manager -> New database to create a new file. However, please note that your old data/passwords will still be lost since they are encrypted with the master password you do not remember, unfortunately.