Check out this free tool provided by Microsoft which was released to fix an inconsistency in the Windows servicing store which may prevent the successful installation of future updates, service packs, and software. This tool checks your computer for such inconsistencies and tries to resolve issues if found. This tool is for Windows Vista, Windows Server 2008, Windows Server 2008 R2, and Windows 7.
Read more here – http://support.microsoft.com/kb/947821