1) Find whatever security program is installed on your machine, and temporarily disable it.
a. It may take some digging to find this option, as many security programs don't like the idea of being "turned off" … look for options like “disable real-time scanning,” “suspend real-time scanning,” or the like. If you’re lucky, right-clicking on the icon in your taskbar will show an option to disable, but I’ve found that option is being included less and less frequently on right-clicking the taskbar icon in security programs.
2) Run services.msc (Start > Run, “services.msc” and hit Enter)
3) Find the “Windows Update” service
4) Stop the service and then start the service again.
5) Run Windows update
6) Install any updates
7) After completing the installation, be sure to re-enable your security program to normal functionality.
Hope this helps.
http://social.technet.microsoft.com/Forums/en/w7itproinstall/thread/ca6ab922-e35e-4cf5-90a6-4d635d83e5ae
