First of all, most, if not all, Linux distributions are free to download. So, if the only reason you're thinking for going with White Box Linux is price, I suggest you look through the "Distro Reviews' on this site and find one that tailors to your likes/dislikes. Other sources of Linux distributions include our host's http://iso.linuxquestions.org
and also, http://linuxiso.org
After a quick Google search I found a guide to setting up a White Box Server at http://www.falkotimme.com/howtos/per...ebox/index.php
. I'm not sure if that's what you plan to do with it (I don't think so, sounds like you want an alternate home OS).
If you look through the distro reviews and decide on Debian, there is a nice guide at http://www.aboutdebian.com
I have no experience with White Box, but after my quick Google search, it looks like a server-oriented linux since google found White Box Enterprise sites.
I can't really help you with dual-booting with XP, as I believe it is different than dual-booting with Win9x, which is what I've accomplished (I'm dual-booting Debian and Windows98SE).