Most of the time this happens with Firewire drives. Most firewire drives purchased are pre-formatted with a FAT32 (MS-DOS/Windows) file system. All Macintosh computers out of the box are able to read these types of drives transparently and they show up as a normal Mac volume.

Normally you can just ignore this unless this is the volume you are trying to recover. If you are trying to recover the drive with an MS-DOS format use VirtualLab for Windows to recover files off of the drive using a PC running Windows and then use VirtualLab for Mac’s ‘Merge Utility’ to give the files their correct file type/creators and resource forks.