Any Vista user interested in trying out the update will be able to do so through a Customer Preview Program on Microsoft's TechNet Web site, said Mike Nash, corporate vice president of Windows product management, in a blog post.
He encouraged most Vista users to wait until the final release of the service pack, scheduled for the first half of 2009. But technology enthusiasts, developers and IT pros might want to try out the software and offer feedback, he said.
Microsoft also began offering the beta to subscribers of Microsoft Developer Network (MSDN) and TechNet, both organizations for developers and IT professionals, on Tuesday.
Vista SP2 includes previously released fixes and is expected to be compatible with applications that run on Windows Vista and SP1. It will also include a couple of other new features, including Windows Search 4.0 for improved search, the most recent Bluetooth 2.1 Feature Pack, the ability to record data on Blu-Ray media natively, Windows Connect Now for easier Wi-Fi configuration, and support for UTC timestamps for file synchronization across time zones.
Microsoft distributed SP2 to a small group of beta testers in October at its Professional Developers Conference.
The second update for Vista comes as Microsoft continues to work on the operating system's successor, Windows 7. Microsoft offered its first pre-beta version of Windows 7 to developers at PDC.