Vista 64 bit, Vista/XP dual-booting

[PIPER]

However, where can I find about dual-booting XP and Vista? My Vista license is upgrade only so I'd actually have to dual-boot XP & XP first, then upgrade one installation, right?

But my main question is if I have to trash my existing installation? I have a load of diskspace free (>50%) so is it possible to create another partition non-destructively?

I had XP installed....bought Vista Ultimate upgrade..put in the disk and it asked where I wanted it....so one install should do it....

Not necessary to trash anything.