I've installed a Seagate Momentus XT drive on a T500, type 2081. It works fine once the mounting tray and rubber shock rails are transferred over.
Be sure to pay attention when inserting the drive. If you install it upside down, the BIOS will not recognize it because it did not seat in the physical connectors in the bay. If the plastic HDD cover won't go on, the drive is probably in upside down.