Right off the bat, this is a bad idea. I mean,. a really bad idea
. Config files have a tendency to vary a lot between distros/versions/DEs, etc...., and you'll end up really hosing your system, without a slim chance of debugging, understanding where things are going wrong and no recovery. The fact that you still want to use 10.04, an unspported, EOL'd distro is also sending out several red flags -- to borrow a regex chestnut, "now you'll have two problems".
Please search within these forums and you'll find this question being asked several times. And everytime the answer is, share a different mountpoint that contains "common enough" files like documents, music, source code, etc., and nothing more.
Then add a link those dirs/files in your respective /home dirs. This will work, iff the username used b/w distros are the same. If you use different usernames across different distros, you will run into file access/file ownership issues very quickly.
So, please do a search within our forums first. And at the risk of sounding like a rebel, I would also recommend ubuntufourms as there is some fantastic discussions on this (as well as other) topics.
tl;dr => The stackexchage thread is what you should follow.
