Not what I asked. I know that. Same hard drive, different partition, or dfifferent hard drives. But if I setup XP first, will Ubuntu automatically notice that so I can set up a dual boot system?
try wubi, it allows ubuntu to be installed and a dual boot to be made but you can uninstall it from the add/remove programs in xp so it is easy to take it off if things don't work out and there is no partitioning needed.