Microsoft wants users of its Windows operating systems to move to upgraded versions of the software, so it's killing a tool that prevents upgrades from automatically self-installing.

"I have some important information for those of you who have installed the Service Pack Blocker Tool for Windows XP or Windows Vista," wrote Brandon LeBlanc, Microsoft's in-house Windows blogger, in a Friday post.

"The Service Pack Blocker Tool temporarily prevents the installation of a service pack through Windows Update, typically for one year after general availability of the service pack. We are announcing the upcoming expiration dates for the Service Pack Blocker Tool for Windows Vista SP1 and Windows XP SP3," LeBlanc wrote.

LeBlanc said the blocker for Vista SP1 will expire on April 28, while the blocker for XP SP3 will expire on May 19.

Despite the tools' expiration, LeBlanc noted that companies that don't want to upgrade to the Windows service packs won't be forced to do so. Users that have the Automatic Updates feature turned on will receive an alert from Windows Updates indicating that an important update is available for installation. Users can then elect to install the service packs or ignore the update.

Users that don't have Automatic Updates turned on will receive the alert only after manually checking for updates in Windows Update.

LeBlanc said Microsoft is urging enterprises that haven't already done so to install the service packs. "Microsoft strongly recommends all customers move to Windows Vista SP1 if they are running Windows Vista or Windows XP SP3 if they are running Windows XP," he wrote.

Software makers typically issue service packs to improve security, stability, and other product attributes.

"Our goal in announcing the removal of the blockers early is to provide you with an early notification to ensure you're prepared to deploy the appropriate service pack when the blockers expire," wrote LeBlanc.

Microsoft's newest operating system, Windows 7, isn't expected to be released in final form until late 2009 or early 2010. A trial version is currently available, though some institutions -- including Georgetown University -- are forbidding its use.