There's a few different ways to do it but they're all pretty ugly. Nothing as simlpe as changing a key and doing an upgrade install.
A fresh install will give you the best chance of enjoying the experience
If you're keen to puddle in your existing setup and try and upgrade then let us know and I'll dig up the link on how to do it. (Can be found at
www.thegreenbutton.com).
Cheers,
Arkay.