I’m fight tis problem too, and found something.
If you bought a pc pre-formatted my book you could be in deep s**t.
The factory is deployed a partition on the hd approx 231 MB it contains (external firmware, and so on)
(i dont know yet what is the purpose of this partition, im in the middle of investigating)
But i supecting few things.
If you plug this external drive in a mac and if it’s reconize it you should start disk utility,(or the system offer you to initialize this disc)
The disk util see the logically possible usable area wich is not equal to the real usable free space because of the 231 MB partition, (my macs didn’t see this partition)
Regarding the problem when the mac can’t see this partition i assume the disk util try to declare the new partition owerlapped on the 231mb factory partition. ( i tried to delete it but no sucess until this time) and this is causing a logical problem for the disk utility.
I tried several tools like: win disk manager, in win7, and 8 beta. (actually the win8 can see the pre made part but not able to delete it, but the left over area is possible to use on)
I tried several linux edition, mandriva, suse, ubuntu, theese are capable to make HFS+ partition but cant see the real free space of the disk. So this way is useless for me.
I tried acronis true image boot cd and i saw there is a “phantom” partition but this tool not able to partitioning (not made for it) the leftover space.
I will try to use the Acronis disk director and will see if any result will be.
I’ll keep posted the investigation.