I was amazed to hear that it is possible to move a disk with an ubuntu (and probably other) linux install on it from one machine to another (different type of) machine and it will still work. Possible spanners in the works are the graphics card (which may need reconfiguring) and network connections which are hooked up to the linux install according to mac address. I tried it this evening - moved a disk and network card from one machine to another and I instantly had a working box that I could ssh in to, although needed some work to get the graphics card recognised (won't go into that here, but CTRL - ALT and backspace is handy for restarting
x-server).