Get another Hard drive, install XP clean and alone, then run them separately. I've heard of dual boot's going awry and not being able to boot either OS.
In some months, i'm stating at the IT-class, where I get some programs that doesn't run with Vista (which i'm using), and they recommend everybody to have XP. I know I can dual-boot my system with both Vista and XP, but I have to delete everything on my harddisk to create another patition for XP. Can I get a program that creates another partition without deleting? Or can I mabye install XP on an external harddisk?