u can have other files but the w7 did needs to be extracted to root of hdd/usb. so if u had other files on the same hdd just make a folder like "hdd files" and put it in there. If you hdd does not boot after u made it 1st boot in bios then check if it shows in bios.
One of my usb to 2.5hdd caddy did not show in bios so i had another adaptor which was sata to usb and i got power from pc's external source.
One of my usb to 2.5hdd caddy did not show in bios so i had another adaptor which was sata to usb and i got power from pc's external source.