Dual-Boot: Vista/XP Pro

Ok so a friend just got a Vista-installed Dell laptop for college. However, the college insist on XP Pro as the OS of choice. Therefore I could just format and install XP, but he likes Vista for home use so I'm thinking Dual Boot is a good idea.

I'v no experience of Vista personally though. I was thinking of going about it like so:

1. Create an image of the HD as it is with Vista installed, onto a CD
2. Formatting the HD
3. Installing XP onto a partition, and then Vista onto another

Ok yeah it's a pretty basic plan.
Anyone care to point out any mistakes i'v made or problems I might come up against? Again itt's basic but sounds like it'l work to me. But again, I'v no experience with Vista so please correct me.. Are their issues with running XP and Vista from the same drive?