Windows 7 is not even available in Beta yet. However, when it does come out, you will be able to dual boot with XP. Your best bet is to use Parition Magic or Partition Commander to set up your disk for you. You can set up dual boot without, but it’s tricky.
It is in beta (I am typing this within it) and It works fine.
When I dual booted it with Vista I used a program called Easy BSD to set up the dual boot. This doesn’t work with xp, But you should probably be given an option.
A great program that can control partitions and multiple OS’s is Acronis Disk Director. It’s not free but i’m sure you could find it on your favourite torrent site.