I have a feeling this has something to do with the post on hackaday...
http://www.hackaday.com/2008/01/03/psp- ... drive-mod/
IMO, I believe it's a fake. I believe It is entirely possible, but some of the statements are out of wack. A 200GB hdd inside the PSP? No way, well, maybe if it was SSD, but most definately not for anything close to under 100$. Plus, it would have to be gutted and reassembled.
I hope you get the thing to work, but from the looks of the questions here, and the post on hackaday, the two just dont jive (pro duo to usb? yet, you're using a hdd? nah).