Installing one more distro should not trash home. But if it's pretty close, but still very different (and yes this makes sense if you ponder it a while) it may trash settings in files by the same name, because home is "touched" during install
Oh - this is rather confusing taken literally
By changing the permissions in Fstab I am able to access the files from XP.
I hope you mean you are able to access the "XP files" from Linux as what ever you do in fstab does not change anything in XP