Hello, there is actually a way of installing xp with vista already installed, unfortunately you will need the Vista DVD to do it along with some software called 'EasyBCD'.
The only other way I can think of having both OS' on your PC would be to use a separate hard drive.
Also, haven't you got the chipset drivers on your motherboard disc? Or aren't you given that either when you buy the system?
If you decide on either of these options and you need some help then let me know.
Regards
Martin