If you want to do a real hd install, the 20GB hd will have to be ext2, ext3, reiser, etc. a supported linux filesystem, not fat32. You may want to partition the 20 GB drive into a 6 to 8 GB linux partition for your knoppix os and other linux specific stuff, and leave the rest as a fat32 shared drive, accessible from both xp and linux.

As far as I know, ntfs support is only reliable for read-only, I've read that if you write to an xp system partition while the os is NOT running, it won't boot anymore (I don't know this for cretain as I've never really used xp, or win2k).

Linux does ogg

HTH

~rock