Flavius

Try this->How do I reset Windows Update components? and this->Description of the System Update Readiness Tool for Windows Vista, for Windows Server 2008, for Windows Server 2008 R2 Release Candidate, and for Windows 7 Release Candidate
and this->An update is available to fix a Background Intelligent Transfer Service (BITS) crash on a Windows Vista-based computer

If still nothing help try disable non -system service (How to perform a clean boot procedure to determine whether background programs are interfering with a game or a program that you currently use
) and again try install updates
if still nothing help try to reinstall Windows Installer ->Windows Installer 4.5 is available