harkaz has been working since September 2013 on the project, which aims to bring together all of Microsoft's official XP updates and patches into a single unified release. It is already available in its third beta but, as ZDNet reports, a Release Candidate will soon be available, ahead of its full release. In a forum post, harkaz explained that Unofficial SP4 is "a cumulative update rollup for Windows XP (x86). It can be applied to a live Windows XP system with SP1, at minimum, installed or it can be slipstreamed (integrated) in any Windows XP installation media." The package includes:

     - Most Windows XP components, including Media Center Edition and Tablet PC
     - Request-only hotfixes
     - .NET Frameworks 4.0, 3.5, 1.1 and 1.0 (Tablet PC only)
     - All post-end-of-life updates for .NET Framework 1.1, 3.5 and 4.0 up to May     2014
     - Ability to scan for new updates (using the Windows Embedded POSReady 'trick', which Microsoft advised against using)