Tiny Empire's fix (force boot) of non booting windows.

http://www.tinyempire.com/shortnotes/files/ntldr_missing.htm

When your computer starts, the BIOS attempts to find the primary hard drive's active partition to read the first sector for the MBR (Master Boot Record), it uses that info to load the rest of the OS. For Windows NT4/2k/XP the NTLDR (New Technology Loader) takes it from there. If you get the "NTLDR is missing, press any key to restart" what's most likely going on is the BIOS either didn't look for the right drive, didn't find the right partition, it wasn't active, didn't find the MBR, or the MBR didn't list NTLDR in the right place, or the location of NTLDR changed.

What to use if for here.

It MIGHT allow you to boot one of these installs on a USB (certainly a CD) and maybe then continue to boot of the device that the OS won't boot from because of the bios.
I have been fighting with a dell trying to get a USB only windows to work.. While I havn't gotten that to run correctly, booting to the cd first forces the computer to then use the USB drive and continue booting.

I'm surprised there isn't a USB variant of this already.