Re: older versions of Windows
Older versions of Windows aren't really a concern, because they won't work without a BIOS. I haven't heard anything about UEFI providing a "compatibility mode" or any other accommodation for older software. Recent Windows software will probably work because MS abstracted all that away in the HAL, but I seriously doubt they'll ship a HAL for XP that speaks UEFI. And no more booting up with that old copy of DOS 6.22, either.