whenver i release a new version, even though i have changed the upgrade code, the installer warns the user that it cannot continue since it's already installed and the user needs to uninstall it themselves first. how can i have the *installer* automatically remove the old version and then install the new version, so the user doesnt have to manually do it? this is very frustrating. any help is appreciated.
You should not change the upgrade code, but rather change the product code to perform a major upgrade. The help article Major Upgrades should assist you.
That code would uninstall the product you specify in PRODUCT GUID. It is InstallScript so you put it at whichever point in your code you wish to uninstall the product. Generally this would be in OnResumeUIBefore or something like that. But for a major upgrade I recommend changing the product code and following the built in propert of IS_MAJOR_UPGRADE.
