The company said not all customers will get the update right away because "Microsoft is distributing the Service Pack in phases to ensure a seamless download experience."

Once SP1 is downloaded to a user's computer, installation will take about an hour, Microsoft has said.

For background on the importance of SP1 to adoption of Windows Vista, see this story, accompanied by more details on how to get the update here.

Microsoft issued a press release to announce the distribution of SP1. It took the opportunity to go back over the Vista sales pitch. The company also touted several statistics about the increasing importance of the PC in the past six years. However, it did not provide an update of the Windows Vista install base, which, when we last we heard an update in January, was 100 million. Perhaps that's coming tomorrow with the company's third quarter earnings announcement.

Microsoft, in this release, emphasized the idea that the PC is at the center of our digital lives.

"... PCs have shifted from being tools primarily for personal productivity and document creation to becoming canvasses for self-expression and connecting and collaborating with others, as well as multimedia home entertainment hubs that function as digital photo albums, digital video recorders and virtual jukeboxes."

Of course that's true. But it's interesting to contrast this language with the meme underlying Microsoft's Live Mesh announcement today, and the Ray Ozzie memo that accompanied it. It's designed to make the proliferation of devices -- both PCs and mobile devices -- more manageable and useful via the Internet.

From Ozzie's memo: "To individuals, the concept of 'My Computer' will give way to the concept of a personal mesh of devices -- a means by which all of your devices are brought together, managed through the Web, as a seamless whole."