Applies To: Windows 8.1
When installing Windows on UEFI-based PCs using Windows Setup, your hard drive partition style must be set up to support either UEFI mode or legacy BIOS-compatibility mode.
For example, if you receive the error message: “Windows cannot be installed to this disk. The selected disk is not of the GPT partition style”, it’s because your PC is booted in UEFI mode, but your hard drive is not configured for UEFI mode. You’ve got a few options:
Reboot the PC in legacy BIOS-compatibility mode. This option lets you keep the existing partition style. For more info, see Boot to UEFI Mode or Legacy BIOS mode.
Reformat the drive for UEFI by using the GPT partition style. This option lets you use the PC’s UEFI firmware features.
You can do this yourself by reformatting the drive using the instructions below, or if you need to preserve the data, use a third-party utility to convert the drive to GPT format.
Many PCs now include the ability to use the UEFI version of BIOS, which can speed up boot and shutdown times and can provide additional security advantages. To boot your PC in UEFI mode, you'll need to use a drive formatted using the GPT drive format.
Many PCs are ready to use UEFI, but include a compatibility support module (CSM) that is set up to use the legacy version of BIOS. This version of BIOS was developed in the 1970s and provides compatibility to a variety of older equipment and network configurations, and requires a drive that uses the MBR drive format.
However, the basic MBR drive format does not support drives over 4TB. It's also difficult to set up more than four partitions. The GPT drive format lets you set up drives that are larger than 4 terabytes (TB), and lets you easily set up as many partitions as you need.
Turn off the PC, and put in the Windows installation DVD or USB key.
Boot the PC to the DVD or USB key in UEFI mode. For more info, see Boot to UEFI Mode or Legacy BIOS mode.
When choosing an installation type, select Custom.
On the Where do you want to install Windows? screen, select each of the partitions on the drive, and select Delete. The drive will show a single area of unallocated space.
Select the unallocated space and click Next. Windows detects that the PC was booted into UEFI mode, and reformats the drive using the GPT drive format, and begins the installation.