Microsoft might have declared Windows XP officially dead in April 2014 but statistics pointing to its popularity (albeit on the wane) means that there's still plenty of demand for a service pack.
No surprise therefore that someone else seized the opportunity. a Greek-based developer called Harkaz has posted an unofficial, unsupported Service Pack, which has been christened Service Pack 4 (or SP4).
The build, currently in Beta 3, was finalised more than 10 weeks ago but has only been posted recently. Note that it is a cumulative update rollup that includes all official Windows XP updates for x86.
Harkaz confirmed that the updates apply to most versions of Windows XP including MCE and Tablet PC. He added "equest-only hotfixes have been included. Currently, Microsoft .NET Frameworks 4.0, 3.5, 1.1 and 1.0 (Tablet PC only) are included in the Windows XP SP4 package. You can also scan for POSReady updates, because the POSReady trick has been included. In addition, all post-eol updates for .NET Framework 1.1, 3.5 and 4.0 until May 2014 have been included".
The 827MB file has yet to reach its "release candidate" status as Harkaz confirmed this week that he is working on the setup information files as well as the catalog file (spcmp.cat).