Windows installer - Remove Previous Versions

http://www.simple-talk.com/dotnet/visual-studio/updates-to-setup-projects/

Excellent link and explains how to unisintall previous versions of your application.

Note that the version number in the article refers to the installer version number that is accessed in the properties window. This must also being at 1.0.0 or above, otherwise the RemovePreviousVersions property won't pick it up as a previous version and won't work.

Enjoy!