If your original installation of the game was a release you downloaded before October 1, 2010, you will have to uninstall it before installing the f40 release. On your PC, go to Control Panel, Add or Remove Programs, scroll down to People Power (and People Power Scenario Builder) and click Remove. Be sure to remove both of them. Then, be sure your version of Adobe AIR is 2.0 or later, and you will be able to install the f40 release. Future releases will not require you to uninstall the old one—when you start to install future releases, you’ll be asked whether you want to replace the existing one, and you just click ‘replace’.