PureXTC is on the right track..

Linux needs a (any) partition and uses other filesystems..
Linux can be installed on FAT(32) but it won't be a good (safe) and fast system..
Most linux systems install on a ext2, ext3 or reiserfs system

Most Linux distro's come with a nice installer that guids you thrue the process..
I don't know about Caldera (never used it)..

Good luck..