Many companies have a sort of a rule about Microsoft: wait until version two or the service pack to install. But that doesn't mean that if the software's already installed, you want the service pack, either. Last week, Microsoft acknowledged the service pack laggards by releasing the Windows Service Pack Blocker Tool Kit.

The small download made available last Thursday will prevent installation of service pack updates sent through Windows Update for Windows Server 2003 SP2, Windows XP SP3, and Windows Vista SP1. It will be valid until March 2008 for Windows Server 2003 and for 12 months after release for the other two operating systems.

Microsoft is planning to release Vista SP1 soon; a release candidate of the service pack is available for public download. Windows XP SP3 also is on the way. The Windows Server service pack was released in March 2007.

There are any number of reasons a company wouldn't want to install a Windows service pack. Companies will likely want to test the software before rolling it out, and may want to roll it out selectively so that corporate networks don't become overwhelmed with traffic.

The toolkit doesn't block installation of any of the service packs from a disk or from the standalone download packages, only stopping delivery of service packs through Windows Update. That also means that the many companies using Windows Server Update Services won't be affected, though they already can manage how updates are distributed.