From Windows 8 CP, I decided to see if I could get a UFD to boot using exfat for the filesystem. Since I have only smaller UFDs, I decided to just copy the system files (bootmgr, bootnxt, c:\boot\bcd) to the UFD and see if my PC would boot my existing installs right from UFD.
First used diskpart in Win8CP;
DISKPART> select disk 9 Disk 9 is now the selected disk. DISKPART> clean DiskPart succeeded in cleaning the disk. DISKPART> create partition primary DiskPart succeeded in creating the specified partition. DISKPART> select partition 1 Partition 1 is now the selected partition. DISKPART> active DiskPart marked the current partition as active. DISKPART> format fs=exfat quick 100 percent completed DiskPart successfully formatted the volume. DISKPART> assign DiskPart successfully assigned the drive letter or mount point. DISKPART> exit Leaving DiskPart...
Then I booted to my Windows XP install and stole the boot files and BCD from my Windows 7 (the system) partition. My Windows 7 partition is the one I use for bootmgr, bootnxt, and \boot\bcd
I also copied some stuff maybe I needed, maybe not, \boot\en-US directory, BCD.LOG files in \boot, BOOTSTAT.DAT, \boot\Resources
Anyway, went into BIOS, changed HDD boot order to said UFD, and it booted to the BCD menu fine. I was able to boot into Windows 7 or Windows 8.
When booting it showed the old Vista booting "progress" bar (the green bar thing that is animated).
In Windows 7 the UFD can be ejected and everything is fine (maybe because the real BCD is there), but in booting this way to Windows 8, once the UFD is ejected the system freezes until it is reinserted. I think this is by design allowing the "Windows to Go" feature.
that's all for now...