Microsoft has confirmed it has finished working on Windows XP Service Pack 3 (SP3) and released it to computer makers and volume licensing customers.

"Windows XP has released to manufacturing," said Chris Keroack, the service pack's release manager, in a message posted to a TechNet support forum on Monday around 1 pm EDT. "Windows XP SP3 bits are now working their way through our manufacturing channels to be available to OEM and enterprise customers."

Last week, the Neowin.net website reported that Microsoft would declare XP SP3 as RTM (release to manufacturing) on Monday, and would follow up by posting it for download on its website and through Windows Update at the end of April.

Keroack confirmed the 29 April date on Monday. "We are also in the final stages of preparing for release to the Web on April 29, via Windows Update and the Microsoft Download Center," he said.

Users will be able to update their XP systems to SP3 starting next week, but they will have to select the optional download in Windows Update or download a much larger-sized standalone installer from the Microsoft site. The company won't begin pushing XP SP3 to users who have Windows Update set to automatically download and install important patches or fixes until "early summer," said Keroack.

Some sources have been more specific about when Microsoft will flip the Automatic Updates switch. TechARP.com, a Malaysian website that correctly predicted several release dates for Windows Vista SP1, said last week that Microsoft will begin pushing XP SP3 on 10 June.

Microsoft has set 30 June as the end of XP's availability to major computer makers and in retail, just days after SP3 will conceivably hit Automatic Updates. Although CEO Steve Ballmer said last week that "we will listen" to customers who want the OS's lifespan extended, he made no promises. Microsoft did not immediately reply to questions today about XP and SP3, including whether it would grant the operating system another reprieve.

Today's RTM announcement was considerably lower-key than when Microsoft trumpeted the availability of Vista SP1 earlier this year. Then, Mike Nash, vice president of Windows product management, posted a long blog entry to broadcast that SP1 had shipped.

By comparison, the TechNet forum used by Keroack is unknown to most users.