This seems to be an old problem, perhaps someone has now found a solution:
I have a Toshiba 150GB NTFS external USB 2.0 hard drive I used as backup when I had XP, but now I have W7 Pro 64-bit (SP1), and the Backup programme cannot see the drive.
It shows in Explorer, it's working fine, has write permission, but isn't in the Options list in Backup.
Drive is 18 months old. W7 found and installed the USB driver for it.
It's hard-wired, I do not have a network.
Also, Windows cannot format the drive.
I changed the drive letter from F that W7 named it, to Z, no go. All I see in Backup is the C drive and the DVD.
It's been suggested that I uninstall all the USB drivers and reboot and let Windows reload them, but I have a USB mouse and keyboard so if I do that there is no way to control the computer.
How can I make the external drive visible to the Backup programme? Any assistance much appreciated.