A day after Microsoft accidentally sent a patch to some users running the Windows Vista operating system, the company updated the preview release of Vista Service Pack 1 (SP1) to a small group of testers, the company confirmed Thursday.

"Microsoft [has] released the latest prerelease build of SP1, Windows Vista SP1 RC Refresh, to approximately 15,000 beta testers," a spokeswoman said in an e-mail this morning. "This group includes corporate customers, consumer enthusiasts, software and hardware vendors, and others. The code is not available for public download."

Four weeks ago, Microsoft made Vista SP1 Release Candidate available to the general public for the first time. The 15,000 testers, however, had earlier beta versions to work with, as well as this most recent update.

The company has slated Vista SP1 for final delivery this quarter, and Thursday said it remained on track. "We are still on schedule to deliver SP1 RTM in Q1 [calendar year 2008]," said the spokeswoman.

In a separate issue, though, the company Wednesday admitted a snafu in a Windows Vista update it issued Tuesday to prep PCs for the later release of SP1.

The update, which is described in the support document KB935509, was one of three prerequisites for SP1 unveiled Tuesday, and was supposed to end up only on Vista Enterprise and Vista Ultimate machines, since it targeted BitLocker, the full-drive encryption technology bundled with those premium versions of the operating system. Instead, the update was also offered to PCs running Vista Home Basic and Home Premium.

"We had a small number of early customer reports, that in some cases, this update was being offered for installation on all Windows Vista editions versus just Ultimate and Enterprise," said an anonymous poster on the Microsoft company blog devoted to the Windows Update development team. "For systems set to download and install updates automatically, the update will not install even if it has already downloaded, so most people will not be affected by this," the post continued. "Customers who installed the initial release of the update on editions other than Ultimate or Enterprise should not be concerned as the update will have no negative impact on their systems."

Although some users on Microsoft's support forums wondered why they had seen the BitLocker patch when it didn't apply to their machines, no one running Home Basic or Home Premium had reported problems as of midday Thursday.

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