After a week-long delay to take care of a last-minute compatibility bug, Microsoft Tuesday gave the green light to Windows XP Service Pack 3 (SP3).

The service pack, undoubtedly the last for the aged operating system, was released Tuesday to Windows Update as an optional upgrade, and standalone executables were added to Microsoft's download servers.

To paraphrase -- and, at the same time, contradict -- Winston Churchill, although this isn't the end of Windows XP, it's certainly the beginning of the end. But we come not to bury XP, but to praise it -- and to answer a few last-minute questions now that it's really, truly, yes-indeed available to anyone who wants it.

Can I really get Windows XP SP3 now?

Yes. You can grab it from Windows Update (WU) or download a standalone installer from Microsoft's Web site.

Will Windows Update automatically download and install XP SP3?

Not yet. Instead, you must choose "Windows Update" from the Start Menu, then click on either "Express" or "Custom." In both cases, WU will offer XP SP3. In fact, it will offer SP3 before any other update or patch.

To start the 30-minute process, click the "Install Updates" button.

Microsoft has said it will flip the switch for automatic download and install -- the setting that most users have ticked in WU -- sometime this US summer. Others have speculated that the push date has already been slated for June 10.

Where's the standalone installer?

As is its policy, Microsoft has also posted a much larger installation file that doesn't require WU. The XP SP3 standalone installer, which weighs in a 316MB, can be found here.

Anything I should know before starting the update?

You could just jump into the fray, but Microsoft has a whole list of steps it recommends prior to installing XP SP3. The list talks about prerequisites and hard disk requirements, mentions (but doesn't recommend) disabling anti-virus protection and suggests several other moves, including making a full backup before you begin.

That document is also a good resource, or at least a good starting point, for troubleshooting a balky XP SP3 update; it includes information on a host of potential error messages.

You also need to uninstall any now-obsolete release candidate or beta of SP3 that you've stuck on the system. We covered that in an earlier FAQ under the section "Do I need to prep my PC for the final version of SP3 if I've installed one of the early versions?"

Anything else?

Yes. Microsoft has warned users of Internet Explorer 7 (IE7) that they won't be able to easily revert to the older IE6 once they've upgraded to XP SP3. And in other browser news, the company's also told users who have installed IE8 Beta 1 that they won't be seeing SP3 on Windows Update.

To do otherwise, according to a long post to the IE development team blog, would invite stability problems.

Microsoft recommends that users who want to retain the ability to downgrade from IE7 to IE6 should uninstall the former before upgrading to XP SP3. Once Windows XP has been updated to SP3, users can then install IE7 and if necessary, later restore IE6. IE8 Beta 1 users should also uninstall the preview before upgrading, Microsoft says.