As expected, Microsoft released Windows Vista Service Pack 1 (SP1) to Windows Update Tuesday, making it available to most, though not all, users.
It also posted a much larger standalone installation package to its download site this morning. The installers weigh in at 434MB for the 32-bit version and 726MB for the 64-bit edition.
"Today, you can now download Windows Vista SP1 via Windows Update," said Nick White, a Vista program manager, in a post to a company blog that the team uses for most announcements.
The appearance of Vista SP1 on Windows Update -- where it will remain an optional download until sometime next month -- was not a well-kept secret. Late Monday, Microsoft inadvertently confirmed that SP1 would hit the update service on Tuesday; before that, however, others, including the Malaysian Web site TechARP, had correctly pegged March 18 as the delivery date.
Most Vista users have been unable to obtain the first major update to the OS, even though it was finished in early February and shipped to computer manufacturer. Since then, SP1 has been released only to certain segments of Microsoft's customer base, including businesses with volume licensing agreements, and IT professionals and developers who subscribed to the TechNet and Microsoft Developer Network services.
The company explained the delay by citing problems with some hardware device drivers, which balked at reinstalling during the update. At the time, Microsoft said it needed additional time to work out ways to block systems with those drivers from getting SP1.
Today, White warned that some users won't see SP1 on their Windows Update lists because their machines have one of the defective drivers. "Windows Update will recognize PCs with drivers that may be problematic and postpone offering SP1 to those PCs until it has installed corrected drivers or other applicable updates," White said. "Either way, Windows Update works to detect whether or not your system is ready for SP1 and not offer it to you until the time is right."
Updated drivers for users who are currently blocked from getting SP1 via Windows Update will be available in "a few weeks," White added.
According to earlier announcements, Microsoft plans to roll out SP1 in mid-April to users who have Windows Update set to automatically download and install fixes.