Dual Boot - will clean install of Vista upgrade kill my original XP installation?

Hi

I've just bought the retail Ultimate upgrade but not yet installed it.

I'm currently running XP Pro and planned to do a clean install of Vista and
dual boot to XP when needed.

But I've just read in another NG that the upgrade to Vista will void the
activation of XP* and render it unusable ( *that is if XP is the upgrade
version rather than a Full version)

Is this correct?

If it is then MS are going to create a lot of new enemies if they alienate
people like myself.

Having paid £250 for Vista ultimate upgrade I don't expect it to kill my
existing system!

I'd appreciate some clarification on this and hope its untrue!

Thanks for any info.

Ian