You could try tsclient which is something akin to remote desktop featured on winxp. This would mean you would need to run a terminal server (assuming knoppix still has this in the latest versions) on your uncle's computer.
I haven't tested this feature of terminal server, but I do use the tsclient which works nicely in a window on the desktop for fixing the winxp machines on my home network.

HTH,

Durand