I created a ticket for you; an email should be in your inbox.
When the operating system sees a drive, but it isn't found in Mozy. There may be a couple of reasons why it doesn't show up.
1) It might be a NAS device. If the drive isn't connected through a USB port, but rather connects through a network cable, then you would need to connect to it as if it is a network device to a shared folder.
2) The USB device is considered a removable device by Windows. If this is the case, Mozy won't see it. This counts for USB thumb drives, and other removable media. Most of the time, drives that are connected through the USB port are seen by Mozy.
3) Possibly, the drive is formatted as FAT32 and not NTFS and isn't being seen somehow.
I would like to remote in and have a look at it and see what might be causing your drive to hide from us...
MOZY backs up file to it (as a local backup). The problem I have is that I cannot get MOZY to backup (other) files found on this USB drive (which are not on my hard drive) and add these files to backup on your servers.