I've updated our article to go into further details for MacBook and MacBook Pro owners. Unfortunately, with only one drive, the process becomes more complex. You'll need to wipe out the drive first and use Disk Utility to triple partition the drive using the GUID option (supporting both EFI and MBR). Then you have to re-install MacOSX. Then install XP by booting from the XP CD. Then install Vista from its DVD. Then you have to edit either XP or Vista's boot.ini file (Windows wants to be the last partition on a drive and obviously they can't both be last). The boot.ini is used to change boot order among other things.
I hope that the final version of Boot Camp, due out with Leopard, supports more partitions to make this easier for MB/MBP owners!
-------------------- Lisa Gade Editor in Chief, MobileTechReview