Microsoft confirmed Wednesday that it delayed the rollout of Windows XP Service Pack 3 (SP3) because changes to the operating system can corrupt data in the company's retail point-of-sale and store management software.

The company has also suspended automatic distribution of Vista SP1 as well as XP SP3. "Yes, we are temporarily holding any additional automatic distribution of Windows Vista SP1" said a spokeswoman.

Tuesday, Microsoft postponed the expected release of XP SP3 because of what it called a "compatibility issue" between the OS and Microsoft Dynamics Retail Management System (RMS), point-of-sale and store management software designed for small and midsize retailers. When it announced the service pack's delay, however, Microsoft did not spell out the specifics of the bug.

In fact, a Microsoft representative had outlined the problem in a post to the RMS support forum five days earlier, on April 24. "The Microsoft Dynamics Retail Management System (RMS) Development team has identified problems when Windows Vista SP1 is installed," said Tom Berger, who identified himself as a Microsoft online support engineer. "Windows Vista SP1 may cause data loss and corruption in Microsoft Dynamics RMS databases."

According to Berger, Windows Vista SP1 changed the way Microsoft SQL Server handles some database records, specifically those that include information from multiple tables. "All users who have applied Windows Vista SP1 will be affected," he added.

A Microsoft spokeswoman on Wednesday acknowledged that the same problems affected RMS users running XP SP3.

The company is also working on filters to block machines running RMS from being offered either Vista SP1 or XP SP3; it will resume automatic delivery of Vista SP1 and add XP SP3 to Windows Update once those filters are in place.

In the meantime, Windows Vista users can upgrade to SP1 by manually selecting it from Windows Update -- it hasn't been removed, only suspended from automatic download and installation -- or downloading a standalone installer from the Microsoft site.

Although Windows XP users have no similar official alternative, some have uncovered a standalone installer for SP3 buried on Microsoft's servers, and have been posting links on the TechNet support forum. Although the installer -- available in several languages, including English, German and French -- was vetted by numerous users who said it was identical to the finished version released earlier to TechNet and MSDN subscribers, Microsoft would not confirm that the links led to sanctioned files.

"In this particular case, it's possible that some third-party websites are linking to the Windows XP SP3 software that we have published for MSDN and TechNet subscribers," a spokeswoman said in an e-mail. "Since we cannot confirm the source of every link that third-parties provide, our recommendation is that customers wait until we've published Windows XP SP3 to Windows Update and the Download Center."

Microsoft's record with Windows service packs has not been impressive. Vista SP1, for example, was held from most users for six weeks because of balky device drivers, and the company initially blocked paying subscribers of its TechNet and Microsoft Developer Network (MSDN) from downloading either Vista SP1 or XP SP3.

Microsoft has not divulged a timetable for resuming Vista SP1 on Windows Update, or offering XP SP3 for the first time. It also has not set a schedule for delivering a fix for the RMS bug.