From Wikipedia…
As of 2010, most current OSs support GPT, although some (including Mac OS X and Windows) only support it on systems with EFI firmware.
Usually you will run into this when you use a disk that has been formatted on a *nix system and try to mount it under windows. You will notice in Disk Management that it will be labeled “GPT Protected Partition” and be unreadable and even unmountable.
If you don’t care about the data on the drive you can use the “clean” command in the windows “diskpart” program.
- Type in “diskpart” on a command line.
- Then do a “list disk” to identify the disk you want to work with.
- Then “select disk x” (in my case it was “select disk 1″).
- Finally bust out with then “clean” command.
- Head back to Disk Management, and find the now “unallocated” disk. Right click on disk info, select “Initialize Disk”.
What this will do is zero out sectors that are part of the MBR or GPT partition map. Oh yeah all data will be lost… Did I forget to mention that? Your disk will now be mountable and usable in both *nix and Windows systems.

