When you boot from the install DVD, there will be an "options" buttons near the bottom of one of the first few screens. From there, choose "Archive and Install" which will give you a clean start but preserve almost all of your applications.
EDIT: While we're talking about this, though, reinstalling is NOT the only way to change the "short" name. There is a tool for doing this. The computer name and user long name are easily changed in System Preferences. I've used the short name utility several times in the past for various users and it saves quite a bit of time.