Unofficial, of course. Remember all those unendorsed service packs for Windows 98 and 2000? Windows XP Service Pack 4 carries forward this tradition, and is now currently in its third beta.
A release candidate is to be available in the near future, ahead of its full release. Developer harkaz has been working on this unified release since September 2013.
Microsoft may have moved away from the service pack concept — even the upcoming Windows 9 is being primed as the last standalone version that will be updated at a steady pace with new features. But that is not stopping fans and users of the now ancient OS from keeping it in tiptop shape.
The unofficial version of Windows XP Service Pack 4, as it is known contains the operating system with all the required cumulative updated rollups injected. Up until May 2014.
It can be applied to a live system that is running at least Windows XP SP1, or slipstreamed (that is to say, integrated) in any Windows XP installation media.
And just in case you were wondering, it is only available in x86 form, which is 32-bit, though it has the ability to scan for new updates using the registry hack trick, which Microsoft clearly warned against.
Speaking of warnings, there is no way Redmond will be supporting this, and users that opt to deploy this unofficial Windows XP Service Pack 4 will be doing so at their own risk. But it does show that second most popular OS on the planet still has an active and vibrant developer community.
More on this upon release.