Microsoft Corp. posted a tool to its download site today that will block automatic installations of several upcoming service packs, including Vista Service Pack 1 and Windows XP SP3.

The download includes three versions of the tool — an executable, a script and a group policy template — that prevents the service packs from reaching PCs via Windows Update, Microsoft’s default update service.

The tool blocks Windows Vista SP1, Windows XP SP3 and Windows Server 2003 SP2 for varying lengths of time. Vista SP1 and XP SP3 can be blocked for as long as 12 months after the service packs are released in final form, while the Server 2003 SP2 blocker bars the download only through March 2008.