Microsoft will deliver Windows Vista Service Pack 2 (SP2) to manufacturing in April 2009, two months after it issues a final test version to users, according to a Web site that accurately predicted several Windows ship dates in 2008.

TechARP.com, a Malaysian Web site that nailed the release-to-manufacturing (RTM) dates for Vista SP1 and XP SP3 earlier this year, said that Microsoft will post a release candidate -- the final test version -- of Vista SP2 in February 2009, finish the service pack next April and offer it to users via download from the Web at some point afterward.

The last was necessarily vague, if only because Microsoft has had trouble this year synchronizing service pack RTM dates with availability on Windows Update. It took six weeks last winter to get Vista SP1 in the hands of most users -- and then only after a ruckus when Microsoft initially denied access to subscribers of its for-pay developer services -- and a week to issue Windows XP SP3 in the spring. XP SP3 was delayed because of a data-corrupting compatibility bug with Microsoft's own point-of-sale software.

Although Microsoft issued the beta of Vista SP2 to a limited number of testers a month ago, company officials have so far only committed to shipping the update sometime in the first half of next year.

According to Microsoft, Vista SP2 will include Windows Search 4, Bluetooth 2.1 wireless support, faster resume from sleep when a wireless connection has been broken and support for Blu-ray. Some of those features, including Windows Search and the Bluetooth support, have been available to Vista users for months through individual updates.

The service pack will update both Vista, the client version of Windows, and Windows Server 2008, the company's corresponding server software.

Vista SP2 will require SP1 as a prerequisite, a factor that played to Microsoft's ongoing recommendation that users deploy the first service pack as soon as possible.