The new boot menu is actually a win32 GUI program. It's c:windowssystem32bootim.exe. You can even execute it in normal windows environment. It is equivalent to execute the command “bcdedit /bootsequence {xxxxx}” to set a temporal boot sequence in the next boot and then reboot.
The new bootsect.exe supports to write the boot sector in the exFAT file system. And the new bootmgr can read data from exFAT partition. The format.com in windows 8 can format an exFAT fs with boot sector. And it is easy to boot winpe from exFAT usb key or exFAT hard disk partition. If you rename grldr to “bootmgr” and place it in a bootable exFAT partition, you can boot grub4dos from exFAT now!
Windows 8 supports usb boot natively!!
You needn’t make any change in registry or other place to make windows 8 usb bootable. Just extract install.wim to usb device with imagex.exe and create boot files with bcdboot.exe, then you can setup and boot windows 8 on a usb device.Windows 8 can place pagefile.sys on usb boot device. So a computer can boot with only usb drive without the complaint of no virtual memory.
In usb boot windows 8, when you plug off the usb device. The system will not crash, everything just stops. When you plug in again, the system recovers.
The setup.exe program still cannot install windows 8 to usb device directly. So you need to install windows 8 manually with imagex+bcdboot.
The UEFI boot is user friendlier than previous version Windows. You can boot windows 8 with UEFI even on a MBR disk. It is no need GPT+UEFI, MBR+UEFI is also OK. Just use the /f:UEFI parameter in the new bcdboot to create the UEFI boot files on a FAT16/32 partition, and execute bootmgfw.efi in the UEFI environment.