First, run Revo Uninstaller to remove the old version of the program from your computer. Even if it can't uninstall the application normally, it will force it to uninstall by wiping out all traces of its presence from the system.
After that, try running AdwCleaner or any other registry cleaner from Software Informer database to make sure that there are no leftover registry keys in your system. After the process is complete, reboot your computer and try again. If it doesn't work, update Windows Installer to the latest version.