Thank you again for your efforts on this product. I have been following this for years and it's fun to see it continue to progress.
You talked about fixmbr and such... and thought I'd share how I resolved a 'broken' GRUB MBR when I deleted my linux partition to resize it.
I just resolved some MBR issues using a tool called Super Grub Boot Disk http://www.supergrubdisk.org/
I'm no expert, but I believe it's fixes it by using the GRUB.exe kernel(hence the grub_device and aux_hd variables) and copying the syslinux.bin bootloader and then setting it to chainload the first partition
# dd SOURCE_FILE DESTINATION_DEVICE FILE_OFFSET DEVICE_OFFSET SIZE
dd $(grub_device)/boot/sgd/brs/syslinux.bin ($(aux_hd)) 0 0 300
dd $(grub_device)/boot/sgd/brs/syslinux.bin ($(aux_hd)) 0x1fe 0x1fe 2
Just thought I'd share as it's an alternative to using the XP recovery disk to fix (or workaround) the MBR issue.