Trying to use LtnFW backup

Found this site yesterday when Googling a firmware problem with my SOSW-852S drive. Before I try flashing with the recommended update I would like to back up the existing firmware (PRS7). LtnFW is asking for the binary file name but I have searched my hard drive and cannot find any PRS7.bin files. Anyone know what the .bin file name should be so I can browse for it?
LtnFW does come up with the correct drive but it needs the actual file name to backup.

Thanks and regards,