What I did!
(Make sure you have a PES2008 option file already set up on the 360)
1. Connect the XSATA thingy to the 360 and then connect the HD to the 360. Do not switch on the 360 yet.
2. Run the Xplorer 360 software on the PC.
3. Connect the USB cable to the back of the port in the XSATA...