Windows Vista Service Pack 1 RC is available through Windows Update. Experience the WU based Vista SP1 installation by following 4 simple steps. Windows Vista SP1 RC distributed through Windows Update will be applicable to Windows Vista machines that are running on any of the 36 languages supported by Vista RTM. If you already installed the Service Pack to your machine by using the standalone package, you must uninstall before you scan Windows Update for Windows Vista SP1. Systems running on Windows Vista RTM require as many as three updates before SP1 can be installed. These updates are permanent to your Windows Vista systems. Windows Update will detect your system configuration and offer the prerequisite packages that are applicable to your system