Microsoft has released a non-critical, non-security update to fix a bug in the Windows Update system in certain versions of Windows.
Microsoft found problems in the Windows servicing store which may prevent the successful installation of future updates, service packs, and software. This update is a tool which checks the system for these problems and tries to resolve them. Errors in Windows Update with the following codes are addressed by this update: 0x80070002, 0x8007000D, 0x800F081F, 0x80073712, 0x800736CC, 0x800705B9, 0x80070246, 0x8007370D, 0x8007370B, 0x8007370A, 0x80070057, 0x800B0100, 0x80092003, 0x800B0101, 0x8007371B, 0x80070490.
On Windows 7, Windows Server 2008 R2, Windows Server 2008, and Windows Vista the tool is called the System Update Readiness Tool. The various versions of the update may be downloaded directly from KB947821. Installation instructions are on that page.
On Windows 8.1, Windows 8, Windows Server 2012 R2 or Windows Server 2012 you can use the included Deployment Image Servicing and Management (DISM) tool. Follow instructions in KB947821.
This fix may appear at some point in Windows Update itself, but it is not there as of today.
This update was announced on Microsoft's Description of Software Update Services and Windows Server Update Services changes in content for 2014, dated February 25, 2014. A second update scheduled for that date, Update for Windows 7 and Windows Server 2008 R2 (KB2923545), will "resolve issues in Windows", and has not yet gone live.