Put your real hdd in the system and go into the system restore menu (hold power until turns on and off, then hold again until two beeps) then have nothing else in your console usb wise and then go to system update and press start and select then change your hdd and let it go for a couple of seconds.. then shut the system off and turn it on again with the new hdd still in it and the hdd will work!!.
You can also use the hdd of a ylod ps3 and acess it hdd to recover your files.