The product is still on track to be finalized this quarter, Microsoft said, while offering its standard caveat. "The final release date is based on quality, so we will continue to track customer and partner feedback from the beta program before setting a final date," the company said.

Earlier this month, Microsoft released the first refresh to the release candidate of Vista SP1, first to about 15,000 testers and later to the public.

As for XP, Microsoft said it released (get ready for another mouthful) "Windows XP SP3 RC Refresh 2" to beta testers on Wednesday. Microsoft said it is aiming for a release sometime in the first half of this year, but added: "our timing will always be based on customer feedback as a first priority."