Microsoft Monday finally slapped a "Done" sticker on Windows XP Service Pack 3 (SP3) and pushed it out the door. The designation of SP3 as RTM, for "release to manufacturing," wasn't much of a surprise, given how the company's schedule leaked last week.

But SP3's path has been long and sometimes tortuous -- Microsoft often simply seems to ignore XP, preferring instead to trumpet Vista -- but it looks like Microsoft's aged, and aging, operating system is wrapping up with the release of its certain-to-be-the-last service pack.

Despite the focus on Vista, there have been a ton of questions about SP3.

Fortunately, we have the answers, too.

Can I get Windows XP SP3 today?

Depends on who you are. Microsoft said that it is shipping the code to computer makers and making it available to volume licensing customers.

"SP3 has released to manufacturing," said Chris Keroack, XP SP3's release manager, in a message posted on a TechNet support forum. "Windows XP SP3 bits are now working their way through our manufacturing channels to be available to OEM and Enterprise customers."

So when do I get SP3?

Microsoft said it would put SP3 on Windows Update (WU) on April 29. Starting then, you'll be able to update by calling up WU, then selecting the download.

For several weeks, SP3 will be optional, just like Windows Vista SP1, which still hasn't come out of its manual WU mode.

Wait a minute. I'm a TechNet or MSDN subscriber and I can't get SP3 Monday?

Apparently not. And apparently Microsoft didn't learn a lesson from the February debacle when it first denied Vista SP1 to the IT professionals and developers who pay hundreds annually for the right to download the company's software for testing purposes.

As a recap, two months ago TechNet and MSDN (Microsoft Developer Network) subscribers raised a stink when they weren't allowed access to Vista SP1 after it was marked RTM; Microsoft took nearly two weeks to change its mind and release the upgrade to the services.

A reprise appears in the works. Monday, Keroack told TechNet/MSDN subscribers, "Not yet. This will be available within the next month," when asked on a support forum when the service pack would be available.

What if I want to wait for WU to do the heavy lifting for me?

Just sit tight. Microsoft will begin pushing SP3 to most users -- all those who have set WU to automatically download and install important updates -- sometime in "early summer," according to Microsoft's Keroack.

Unlike Vista, which was held for weeks after it went RTM, XP has no balky device drivers that will prevent users from upgrading in large numbers.

Microsoft didn't get back to us when we asked why it's postponing automatic updating of SP3. But while Microsoft has offered up a vague delivery date, others have pinpointed June 10 as the flip-the-switch date.