Over two months since it was released to manufacturing, and just a week short of the first month since general availability, Microsoft is now showing strong movement on the Windows Vista Service Pack 1 RTM front. Even before Vista SP1 went gold, Microsoft started serving three updates designed to prepare RTM operating systems for the service pack. KB937287, KB935509 and KB938371 were set up to permit a smooth integration of Service Pack 1. KB937287 is the update responsible for throwing some Vista copies into an endless reboot cycle. Microsoft subsequently cut off the distribution of the Servicing Stack Update delivering the Service Pack 1 installation program.

"We are resuming automatic distribution of the SSU tomorrow and provide more clarity on what happened. To clear up any concerns for those of you who have already installed the update: There is no problem with the files that make up the Servicing Stack Update (KB937287); the problem some customers encountered was with the installation process for the update. That means if you already have the update installed, you do not need to uninstall it or install the rereleased version of the update," a member of the Microsoft Update team stated.

Microsoft essentially admitted that it is entirely to blame for the endless reboot loops impacting Vista operating systems following the implementation of KB937287. According to the Redmond company, the SSU is configured to check for pending reboots or additional updates that need to be deployed. A glitch in the installation process told SSU that it needed to reboot in order to wrap up with the deployment, even if that was not the case. This causes the affected platforms to enter a perpetual reboot loop.

"This pre-SSU update helps to ensure a smooth install of the SSU by working to prevent the system from rebooting during the SP1 SSU installation. We also made additional changes to the SSU installer code, so that it checks for and requires the pre-SSU (KB949939) before it will install. These two updates should now install seamlessly through Windows Update, in the proper order, so those of you with WU set to "install updates automatically" who haven't already installed the SSU don't have to take any further action. For those using the standalone download of SP1, the issues we encountered do not affect that method of installing at all," the MU team member added.

Windows Vista Service Pack 1 Five Language Standalone for both 32-bit and 64-bit versions of the operating system is available for download HERE.