Rather than XFree/Cygwin (which is megs and megs of code and fonts), why not just make the following extension:
When the Knoppix CD is inserted into a Windoze machine, it offers to install the TAPwin32 driver, then boots Knopix in coLinux, and runs Xvnc.
The user's browser could be redirected to the vnc Java client on the coLinux and presto - working X! Alternatively, just run the vnc client (all 150K of it) on the host box.
It already stuns most 'doze users that I can reboot their machine from CD and get a nicer environment with access to all their data... imagine the contribution to Penguin power if we could do that without rebooting!