As promised, Microsoft Corp. did not unveil any security fixes for March. But it did push out several other patches it deemed "high priority," including two for Windows Vista.

The last time Microsoft went a month without releasing security fixes was September 2005.

Among the four updates Microsoft pegged as "non-security, high-priority" today were the usual monthly revamp of the Microsoft Malicious Software Removal Tool and new signatures for the Outlook 2003 and Outlook 2007 antispam filters.

One Vista-specific update was also on the list, as was another that affected both XP and Vista.

The first, dubbed "March 2007 Windows Vista Application Compatibility Update," added compatibility "shims" -- code that makes an application think it's actually running on a pre-Vista PC -- for older Windows titles, including Trend Micro's Internet Security, Windows Server 2003 (SP1) Administration Tools Pack and RealNetworks' RealPlayer 6.0.12.

The second was another revision to the Windows Media Format 11 SDK (software developer's kit) code. In the associated support document, Microsoft said that the update corrected a problem that some portable music players had in synchronizing data with subscription services.

The rare no-patch Tuesday caught some security analysts and professionals trying to figure out how to spend their free time.