Blayze, in order to install to XP, you will need to create a BeOS boot disk since XP doesn't use a "real" DOS. Or install to a real partition and use Bootman to boot the Be or Windows partition. You can add Be to the NT or Xp boot menu but personally I like Bootman better and it is much easier to do.
To install to a real partition you can either make a BeOS PE installation CD from the image.be file and use the boot disk or install PE just like normal from Windows with a boot disk after you use whatever Partion manager you have to create a partition and then install Be to that Partition from the Prsonal Edition running from Windows, go to the installer app, and select from: volume your PE is at, then select to: your partition, this will format or initialize that volume. Then the install should run, after install is over it will ask you if you want to install Bes boot manager, at this time I would do that, it is pretty self explanatory. When everything is done you can go backinto Windows and delete the Personal edition.
The nrmal disclaimers here, make sure you backup and have boot disks for XP and BE before doing this because as always when messing with partitions and the master boot record the possibility is that you can hose everything, just my $.02.