Convert GPT to MBR

1. Turn off the PC, and put in the Windows installation DVD or USB key.
   
2. Boot the PC to the DVD or USB key in UEFI mode.
   
3. From inside Windows Setup, press Shift+F10 to open a command prompt window.
   
4. Open the diskpart tool:
   
   diskpart
   

5. Identify the drive to reformat:
   
   list disk
   

6. Select the drive, and reformat it:
   
   select disk <disk number>
   clean
   convert gpt
   exit
   

7. Close the command prompt window.
   
8. Continue the Windows Setup installation.
   When choosing an installation type, select Custom. The drive will appear as a single area of unallocated space.
   Select the unallocated space and click Next. Windows begins the installation.