As said above there is no support in ps3 for reading ntfs formatted hard drives, it will only recognise fat32 formatted drives which is same format as all the usb sticks.

use a prog like http://www.partition-manager.com/
you can then partition a section of the HD to fat32 and the ps3 will see it no probs, there is a limit to the size a fat32 hd can be formatted too (limitation of 32 GB) because any size over that performance is affected so windows made it so you can't format bigger. but 32gb would be plenty of space just for use on the ps3, i do exactly this with my mp3 and music files and it works perfect