I'm going to guess that you mean the external enclosure and not the hdd itself. If you mean the hdd itself, then as Chuck said, you'll find some magnets, small frizbies, and a few bits of stuff that are now junk.
At the current price of hardrives, you'd probably be better off just buying a new hardrive to use inside your computer than to experiment with this drive. Leave the external hdd as it is. Sell it if you don't want an external drive, use it on another computer, whatever. In other words, just leave well enough alone. Unless you're just determined to play mad scientist.