1. read the pdf provided by boot camp carefully!!
2. use minimum windows xp with minimum sp2 installation disk. if you don’t have such an install disk build one your own with nLite. you can install nLite in an virtual-machine in osx and slipstream your win-xp with sp3 install disk there
2.1 if you have an installation disk with special install-commands (unattended installation) like auto-serial no etc. you have to delete the file /i386/winnt.sif from your source and create the installation image without that file. this prevents windows to install on your fat-formatted disk (formatted by boot camp) and you can reformat the disk with fat or ntfs.
3 before formatting be sure to format the right partition (bootcamp/fat) with your specified disk size.
4 if somthing fails you can eject the install disk by pressing the right mouse button while booting. then osx starts normally.