Microsoft will release Windows XP Service Pack 3 (SP3) to computer makers and some IT professionals next week and offer it to all users via Windows Update April 29, reports say.

Although others had previously pegged SP3's release to the last half of April, an internal schedule obtained by the Neowin.net website is the most specific so far.

According to the site, the service pack will debut April 21, when it's shipped to computer manufacturers, offered to volume licensing customers and posted for download on TechNet and Microsoft Developer Network (MSDN), subscription services for IT staff and developers, respectively.

Most users, however, will first be able to obtain SP3 on April 29, when Microsoft lists it on Windows Update (WU) for download.

However, Microsoft won't turn on the automatic download and installation of SP3 until June 10, said Neowin. "This delay should give system administrators an ample amount of time to prepare for the upgrade or simply come up with an excuse for when things go awry," said Neowin.

Company administrators and users have been able to block the automatic distribution of Windows XP SP3, as well as Vista SP1, since December 2007, when Microsoft published the Windows Service Pack Blocker Tool Kit.

In a broad way, Neowin's timeline meshes with the one Microsoft followed when it launched Windows Vista Service Pack 1 (SP1) in February and March.

Although the company held SP1 for six weeks after RTM, or release to manufacturing, because of balky drivers, it posted the service pack to WU on a Tuesday. It also said it would not push SP1 to users who have WU set to automatically download and install fixes until several more weeks had passed. Vista SP1 also reached OEMs, volume licence customers and TechNet and MSDN subscribers before the general public.

Late last month, a Malaysian site that had correctly predicted the RTM date for Vista SP1 as well as that update's release to WU, said that XP SP3 would arrive in the second half of this month, with a first-wave roll-out of the Chinese, English, French, German, Japanese, Korean and Spanish versions.

The last time Microsoft made an XP SP3 move was on March 25, when it posted Windows XP SP3 RC2 Refresh to WU.

Microsoft officials were not immediately available for comment. In the past, however, it has consistently declined to get more specific about Windows XP SP3's delivery date than to say it's slated for the first half of 2008.