There is a size issue, but its not the hardware, its teh software, 8.0 uses the old formatting, HFS, and 8.1 uses the new HFS+ format that lets you use bigger drives and makes better use of these bigger drives. 8.1 update is also free so, go hook it up. You can't go any higher though, 8.1 is the newest OS yoru 575 can use.