Install/Uninstall
When you try to install Districting for ArcGIS, you might get the message, "Another version of Districting for ArcGIS is already installed. Please use Add or Remove Programs to remove the presently installed version before installing this one." But when you try to uninstall the old version in Add/Remove in the Control Panel, it says it's already uninstalled. In this case, run RegEdit and remove the registry entry HKEY_LOCAL_MACHINE\SOFTWARE\AV_REDIST_EXT so you can install the new version.