Shunter, using VMs is a very good idea - wish I'd thought to suggest it! An added benefit is that you can run multiple VMs simultaneously, and they can interact with each other.
The only caveat is that it does require a beefy PC to run them.
Val d'Isere -
Some time ago, I was disappointed to find that you even need to reinstall everything when you move to an identical computer in every respect --- same motherboard, RAM, graphics card etc. The hard drive refuses to transfer over, even though it is sitting in an identical computer. No doubt there's some ROM (?), or whatever, that is different, but I'm just guessing.
It is possible that your drive caddy is in some way slightly different to a standard IDE setup, but I have never, ever had a problem moving an IDE disk from one PC to an identical PC. It just works!
SD