Windows XP Service Pack 3 was supposed to land today for mass download, but I'm afraid this won't happen. Microsoft today explained what's the main reason behind this last moment delay:

In the last few days, we have uncovered a compatibility issue between Microsoft Dynamics Retail Management System (RMS) and both Windows XP SP3 and Windows Vista Service Pack 1 (SP1). In order to make sure customers have the best possible experience, we have decided to delay releasing Windows XP Service Pack 3 (SP3) to the web. To help protect customers, we plan to put filtering in place shortly to prevent Windows Update from offering both service packs to systems running Microsoft Dynamics RMS. Once filtering is in place, we expect to release Windows XP SP3 to the web.

I suppose many of you already know about the leaked Windows XP SP3 download link, but I prefer to post only legit links here. Microsoft is working on fixing the problem and should release Windows XP SP3 to web very soon.