How to delete GPT Protective Partition

Why we need to delete GPT protective partition?

In Windows XP Professional, you cannot access or modify GPT disk, but you can convert a GPT disk to MBR by using the clean command in DiskPart, which will delete GPT protective partition and remove all data and partition structures from the disk.

Warning: The steps below will erase all data on the GPT disk, please backup your data first.

1. You might see HD Drive in GPT status on Disk Management.
2. Go to DOS command line (click on "Start Menu", then "Run", type in "cmd" in textbox, and hit "OK")
   • Type in "DiskPart" in command line.
   • Type in "list disk" in command line to show all disks in this machine.
   • Use "select" to set the focus to the specified partition.
     For example "select disk 1".
   • Use "clean" command to remove GPT disk from the current in-focus disk by zeroing sectors.
3. Go back to Disk Management, you can see GPT disk is "Not Initialized" now. 
4. Within Disk Management, right click on disk info, choose "Initialize Disk", You can see GPT disk is "Unallocated" now.
5. Right click on disk info, choose "New Partition…", follow Partition Wizard and format it. Now you are able to use the disk in Windows XP.

Reference:
http://blog.paulgu.com/windows/delete-gpt-protective-partition/