Truly? It's confusing when you read answers like these (from the WinXP help
center), in relation to upgrading from an earlier version and whether you
have to keep your old version (rather than sell it or give it away):
Yes. Due to the fact the original full version software and the upgrade
version software together constitute a single software program, you will
need to retain your copy of the prior version of the software program
(including all media, manuals and the Certificate of Authenticity) in order
to establish your eligibility for the upgrade license.
It's the "full version software and the upgrade version software together
[constituting] a single software program" that seems to fly in the face of
allowing a dual-boot, which requires them to act independantly of each
other.
If it is true that you can use an upgrade in a dual-boot scenario legally,
it would be good to know, as I may like to do it sometime with a future
upgrade. Any links to official word on this?