I have Slackware, XP, and OSX all booting from the internal hdd on a MacBook Pro. I have posted a rough draft of the instructions on the Wiki (http://www.mactel-linux.org/wiki/HOWTO#Triple_Booting
). I haven't installed the drivers in XP yet, and I also haven't recompiled/installed a fresh kernel so the touchpad is broken in X.
On another note, has anyone tried ndiswrapper with the wifi drivers known to work in xp?