Comment 10 for bug 811485

Adam, you've misread my comment about Windows and MBR. Allow me to rephrase: When booted in BIOS mode, Windows will only install to or boot from an MBR partition table (normally without a GPT, although Windows treats hybrid MBR disks as MBR disks); and when booted in EFI mode, Windows will only install to or boot from a GPT disk (WITHOUT any MBR entries except for the type-0xEE protective entry). Thus, if a disk has an MBR with non-0xEE partitions defined, as Allen reported, and if it's successfully booting Windows, then it follows logically that Windows is booting in BIOS mode on that computer, not in EFI mode, since Windows will not boot in EFI mode from an MBR disk (AFAIK).

You are correct that the GPT spec requires a protective MBR; however, when I refer to an "MBR partition table," I mean a real MBR partition table with actual defined partitions, NOT merely a protective MBR, which is just a dummy data structure intended to keep GPT-unaware utilities and OSes from messing with the disk.