IR*7;m planning a web application, but later the scripting may change, but I donR*7;t want the database structure to change, so for the start I want to get it right.

The application will later have an IM (instant messenger) just like Yahoo/MSN, so what is the proper way to store the userR*7;s information now.
Then later I will find I way of connecting to it.

Note: The registration form will contain: username,password,fullname,email&country

But if you have any knowledge of how is properly done, I will appreciate it.

I`m using MySql/PHP, But the IM will later be written in Python.
Please tell me what I need then I start making necessary arrangement towards it.

Thank you.
Abah