At certain times, if the WindowsUpdateAgent is pointing to an old file (particularly after performing a windows repair since a repair replaces all the newer DLL files with the defaults) or simply corrupted, you may not be able to perform any windows updates.
Reinstallation of the WindowsUpdateAgent is one of the typical troubleshooting steps to resolve such issues.
Here are the steps on how to do so :
- Download WindowsUpdateAgent and save it to C:\ (Yes, the root directory for ease of access)
Windows, x86-based systems
http://download.windowsupdate.com/WindowsUpdate/redist/standalone/7.0.6000.381/WindowsUpdateAgent30-x86.exe
Windows, x64-based systems
http://download.windowsupdate.com/WindowsUpdate/redist/standalone/7.0.6000.381/WindowsUpdateAgent30-x64.exe
Windows, Itanium-based systems
http://download.windowsupdate.com/WindowsUpdate/redist/standalone/7.0.6000.381/WindowsUpdateAgent30-ia64.exe
- Once completed, Click on Start > Run and type in "CMD" without quotes and press enter.
- It should return a DOS looking prompt (well it is DOS)
- Type in " cd c:\ " without quotes to change directory to the root directory.
- Insert "WindowsUpdateAgent30-x86.exe /wuforce" to kick start the reinstallation. Double clicking and attempting to run the EXE on it’s own is not permissible as Windows will not recognize it as a reinstallation.
Hope this helps 
