Running Windows 7 Professional 64-bit. A logical partition was created on my notebook's hard disc, and given a drive letter (I:). For a while, the disc worked as expected, and then I was unable to open it. There was an error that the drive letter refers to a destination which is unavailable. If I use DiskPart, and assign drive letter I: to that volume, everything works again. But only for a while. I've never encountered this before, and would appreciate any guidance about how to prevent it. The other volumes don't have this issue.