I recently installed a 1TB WD HDD in my Vista x64 computer. I went through the normal Disk Management steps, formatted and assigned a drive letter, all of that. Used it for several days. My main HDD was almost full so I moved a few things over. Then, all of a sudden it quit seeing it. It's not listed as a drive in explorer. In Disk Management I can see the partition in the window on the bottom but it's not listed in the window at the top with my main HDD. When I right click on the partition and choose Change Drive Letter it gives me an error say to refresh or reboot but nothing I do will make this work. I do not want to format it because I need the info on the disk. I tried converting it to dynamic but that hasn't really helped. It now lists it in the top window but without a drive letter and won't let me assign one. Any thoughts??