Windows 7 Upgrade Question - Keep XP install?

I’ve been running Windows 7 RC from a separate disk drive on my XP home machine since the RC came out, using the BIOS to boot into either XP or Win7. It has been working very well, so I purchased a 7 upgrade from XP license from Amazon about a month ago. But I have a lot of stuff on my Windows XP install that I can’t possibly test it all for compatibility with Windows 7. I want to keep the fully functional XP install indefinitely in case I need to run some incompatible software or retrieve some random settings/custom configuration files.

Paul Thurott’s Windows Super Site Review suggests this is possible. If I proceed with the upgrade to Windows 7, will I later encounter problems booting into XP? For example will the XP install on separate hard disk all of a sudden start asking for activation, etc.? How have previous Windows upgrades been handled?

Mods: I’m asking about retaining the same legal install of XP on the same machine, not trying to upgrade and get an XP license for free on another machine.

Yes, you’ll break activation. The installer will want to overwrite the XP install, so unless you take an image of XP and store it offline then you wont be able to try this. Why not download the beta and test it with that?