The backup files saved by Sony Ericsson PC Suite, are using the DBK file extension. These files are saved by default in the (C:) > Program Files (x86) > Sony Ericsson > Sony Ericsson PC Suite directory. I don't know if these information will help you to recover them, but you can contact Sony Ericsson for further assistance. You can get in touch with them using
021 401 0401 phone number.
Note: If your PC Recovery software doesn't help, I suggest you check Software Informer database for an alternative solution.