I recently upgraded my Macbook's HDD and cased the original 60GB one. I formatted it with Disk Utility to an MS-DOS file system and used it, switching pretty frequently between my Macbook and my PC. My problem now is that the hard disk works perfectly fine for about a week, then it starts acting up. After I plug it in (it works in the few seconds after I plug it in) and leave it for a short while, it completely refuses to work, and just keeps giving me the spinning beach ball. Worse still, it hangs my Macbook and refuses to unmount. Even after I go ahead and unplug it, Finder will stop working despite my relaunching it and I am unable to restart the Macbook unless I hold the power button down. After formatting the HDD, it works fine again. Unfortunately, after about a week or so the same problem occurs. I've been through this cycle three times now, and I'm getting pretty annoyed. I really hope someone can help me out with this. I've tried looking online for solutions but I haven't been able to find any. Many thanks in advance.