Error: "couldn't unmount disk" keeps coming up when formatting external HD to eXFat I have a WD "my Passport" external HD that is currently formatted for a PC and I would like to format it to eXFAT. Every time I hit "erase" in disk util it just comes up with the error "couldn't unmount disk". Btw, I am running on Maverick. Can anyone help me with this please?
I had the same problem with the same drive. I finally got it to work by rebooting from the recovery partition and formatting it using the disk utility option.