Tracking Backup methodology

I am running an S1, and touchscreen from a PC, and want to look at the best way to implement tracking backup.

I know that I can network a second PC to my main, and Vista will spread the processing between the two. I’ve also read that two licence dongles are desirable.

If however I only have the one licence dongle, can i switch it from one PC to the other in case of a failure? I would also need to switch the S1, monitor and keyboard and mouse etc too.

If switching the dongle and hardware over on the fly is possible, how are people handling the hardware switching between the two PC’s? Will a simple KVM work, and will Vista cope with the license dongle being switched from one machine to the other (it’s currently installed in the S1).