A: Here are some tips for installing Windows to a UEFI machine. I just went through this today and I learned quite a few things that hopefully will save you some pain.

  1. A UEFI system can't boot from NTFS, only FAT32. This means if you're booting from a USB stick to install the OS, you need one formatted with FAT32. See my recent FAQ of 11/29/12, "Q: How do I create a bootable USB stick that can install to a UEFI system?"
  2. A UEFI system can boot only from a GPT disk, not MBR. (A BIOS system can boot only from an MBR disk and not GPT, which is why you can't take an OS disk from a BIOS system and put it in a UEFI system and expect the system to boot.)
  3. Most UEFI motherboards come with a Compatibility Support Module (CSM), which is enabled by default. It makes the motherboard actually look like a BIOS system, allowing it to boot from NTFS and MBR disk--but you lose the UEFI features and are essentially just using BIOS. If you want to run your system as UEFI, you need to disable the CSM via the motherboard's interface (see the screenshot below) before you try to install Windows.
    ueficsmdisablesml
    Disabling CSM
  4. Graphics cards need to support UEFI Graphics Output Protocol (GOP), to be able to show information as the computer and OS starts. UEFI GOP replaces the old VGA format most graphics cards use. I used a brand new Radeon HD 7950 that didn't support UEFI GOP. This meant that after I disabled the CSM, my screen was blank at Power On. I had to remove the graphics card, plug a monitor onto the motherboards internal graphics socket to install the OS, and configure the motherboard. After the OS was installed, I installed my graphics card again and connected my monitors to it, but then I couldn't see the computer startup or OS load--the monitors only become active when boot has completed! If I needed to access the UEFI for configuration or the Windows boot, I would need to remove my graphics card and connect a monitor directly to the motherboard connector again (or set the onboard graphics to the primary device). Firmware updates for some graphics cards should be released in the future, adding support for UEFI GOP.
  5. Because UEFI requires a GPT disk to boot from, whatever disk you install to must have all partitions deleted from so it can be configured as GPT. It needs to show as a complete Unallocated Space, as the screen shows below.
    win8uefiinstall1sml
    Windows 8 UEFI Installation

    Select New on the Unallocated Space, and four partitions will be created, as the screen shot shows below. This means your system is UEFI, and its been configured as GPT
    win8uefiinstall2sml
    UEFI Installation Screen Showing Partitions

    The Recovery partition is NTFS, and it holds the Windows recovery information. The System partition is FAT32 formatted and contains the EFI system partition that the computer will boot from. The MSR is the Microsoft Reserved Partition (which is space Microsoft might want in the future for certain disk operations such as converting from basic to dynamic). Last, there is the actual NTFS boot partition.
  6. Your UEFI system can boot only from a device that has an EFI boot loader, so after the CSM has been disabled, the only boot devices that are listed will be UEFI aware. I had to insert my USB boot stick in one of the USB ports at the back of the motherboard, and not through the front panel connector, which was odd. The Windows 8 installation files have the EFI boot loader in the efi\boot folder of the install media, which will automatically be found. If on the boot menu you see all your normal drives and USB sticks, then you have compatibility mode still enabled in the BIOS and aren't running in true UEFI. Below is what you should see with Windows installed and a UEFI USB boot stick inserted to install an OS.
    win8eufiinstall3sml
    Windows 8 Boot Manager
  7. If your UEFI supports Secure Boot (UEFI 2.3.1, which at time of writing isn't available), then you should disable Secure Boot during the OS installation, then enable once the installation is complete.

After all of that, and Windows is installed, msinfo32 will show the BIOS mode as UEFI, not legacy.

uefidonemsinfo32sml
BIOS Mode as UEFI