I had used it before with this computer, for a backup in January probably, but I went to use it to back it up again recently, and it did not work. It does not show up anywhere on the computer, though the drive lit up and started. It's a Seagate Expansion 500 GB USB 2.0 Portable External Hard Drive. It does not show on disk manager. When I plug this into the USB, it shows a yellow flag next to Intel(R) ICH9 Family USB Universal Host Controller-2934 and next to Intel(R) ICH9 Family USB2 Enhanced Host Controller-293A. These work with every other USB device I have tried, though. Seagate says if it worked before then it's not their problem. Does anyone have any ideas?