Microsoft on Thursday released the first major update for its Windows Vista operating system to its automated download service, meaning that Vista users could receive the update by default as early as today if they have the service turned on.

Windows Vista Service Pack 1, as the update is called, has been released in English, French, German, Spanish, and Japanese versions, according to Microsoft.

There is a caveat, however.

Microsoft is dribbling out Vista SP1 to home users in small batches -- so it may not be available as an automatic update for some for several weeks. "We'll be distributing the service pack slowly so that we can help Windows users have a good experience," said Chris Flores, Microsoft's official Vista blogger, in a Thursday post.

Users who want Vista SP1 right away can download it manually from Microsoft's Web site.

Vista SP1 includes a number of important performance and security enhancements for the Windows Vista operating system. But it's also not without its problems.

Microsoft has yet to finish ensuring that Vista SP 1 will work properly with all of the keyboards, printers, mice, and other peripheral devices commonly attached to personal computers.

Such peripherals use bits of software called drivers to communicate with the host computer.

Vista SP1 won't install some device drivers correctly, Microsoft has conceded. The company says the issue is confined to "a small number" of drivers. The list, however, includes drivers for an Intel chipset that's found in thousands of PCs and laptops.

Windows Vista SP1 has been hit other compatibility issues.

Adobe's Audition audio production application crashes on computers running the service pack, according to software researchers at NeoSmart.

NeoSmart said the problem is caused by a conflict between Audition and the way Vista SP1 implements a Windows security feature known as Data Execution Prevention. DEP is designed to prevent exploits that rely on memory buffer overflows.