Booting from an external USB CD

Here's the setup.

Presario 2100. The internal CDrom is present but DOA. XP resides on the complete HD. (single Partition)

I have an external USB CD drive and both knoppix 3.7 and 3.8.

I can get the base KNOPPIX: prompt if I set the bios (just updated) as follows:

Legacy USB Spport: ON
Boot Order: CDROM, Removable Device, HD, etc

what occurs:
I enter whatever cheatcodes I am tryuing at a given moment.
The screen shows that the .gz files are expanding.
screen blanks and refreshes with white text warning that a particular bridge is experiemental
loong pause during which the USB CD goes to sleep
USB scan starts.
SOme text appears too quickly for me to read

then it says "KNoppix file system not found." and I am left with a prompt and a couple comands that I really dont understand

I have tried just about every cheat code that seems relevant from the cheatcodes.txt. toram, fromhd=/dev/uba1 (or cda1?) bootfrom=/dev/uba1

I am downloading a new iso to try sticking it on the hd as a raw.iso file and trying to boot from it.

any other suggestions?

ah HA!

If I use 3.7 and boot with bootfrom=/dev/scd0 it is successful.

If I use 3.8 or *even* 3.7 with the knoppix26 cheatcode it tells me to piss up a rope.

So apparently I need to either:

figure out how that bootfrom is replicated in the 2.6 kernel OR just use the 2.4 kernel in knoppix 3.7