You might look into Smart Boot Manager, available from http://sourceforge.net/projects/btmgr/ - according to the docs (I've not used it, but it looks handy), you boot from a device with it (say a floppy - it is less than 50k), and it enumerates the devices on your computer that can be booted from, not depending on the BIOS. It seems that you should be able to put whatever boot image you want on your thumb drive and boot from that through SBM.
(no subject)