Setup and Deployment

Question

I am familiar with creating setup packages and their is an option to look for previous versions. Let's say that I install Version 1 on a client computer. If I have Version 2, when installing it, a message appears that I need to un-install Version 1 before it can install the new version. My question is this, does anyone know how to automatically make a newer version automatically override a previous version? (ie. When installing a Windows Update, you dont have to un-install previous updates to install the latest one.) Please help....