Legally use XPM CD-key to install virtual XP?

For example, I want to use my XPM cd-key not on Windows XPM, but VirtualBox XPM. Just wondering...

I just got off the phone with Microsoft and it IS legal to use the Windows XPM cd-key with another virtual machine.

Hmmm....I expect that you are talking about the cdkey file that comes with XP Mode once it's installed? I'm pretty darn sure that I tried a clean install using XP media and they key and it would not accept the key as valid during the install.

Can you confirm that this worked elsewhere????

I can't confirm whether it'll work or not in that way, but it is legal if you get it to work by other means.