To share users, settings, etc, you'll want to set up /etc/fstab so that /dev/hda4 is mounted to /home. The UNIX filesystem is beautiful because all of your personal files, and the files of all other users, are stored in /home, so it can be easily shared.
There is a good page called "How to edit and understand /etc/fstab"
on tuxfiles that can show you how to do this.
Simply, it should be similiar to:
/dev/hda4 /home ext2 defaults 1 2
I'm not sure about this but some of those distros you mentioned might have graphical tools to manage fstab. But if in doubt do it manually!
I hope this was helpful.