I am trying to format a new Seagate 2tb external I purachased for use with my Mac. It is currently FAT. In disk utility, if I try to erase the current partitions, I get "file system formatter failed." If I try to create 2 partitions (as someone suggested) that are 930GB or so each and format them for Mac, I get "The underlying task reported failure on exit." The original "disk1s2" partition is greyed out; I assume that means it's locked and can't be deleted? How do I delete it?