Following disk failure and XP re-install, my external USB hard disk does not appear when I right click My Computer. It does, however, appear in device manager, which reports that it is working correctly. Obviously, as it has no letter and I cannot see it, I cannot access it. In device manager, when I go to it's properties and look at Volumes, Unallocated space is 476938 MB [the total disk capacity.] Is this where the problem is, and how do I resolve it?