I bought a My Passport Ultra 1TB about a month ago, and have successfully used in on my pc, but I can only view files on my mac. The disc is formatted MS-DOS (FAT). I am unable to verify for errors or reformat the disc. Any suggestions?
If you are able to see the files on your Mac, that means that the drive is showing as read only. However, you should be able to see the drive under disk utilities and should be able to reformat the drive.
Take the information our of the drive and use the disk utilities to reformat the drive.
See if the following links helps.