If you find that Windows Update refuses to install most patches, you can register its missing DLLs yourself. This can be accomplished by manually entering seven commands (shown in Step 2, below) at a command prompt. If you need to run the fix on multiple machines, it's easiest to use a batch file, as Steps 1 through 5 explain:
Step 1. Open Notepad (or any text editor).
Step 2. Copy and paste the following command lines into the Notepad window (the /s switch runs the commands silently, freeing you from having to press Enter after each line):
For those of you like myself that this didnt work for
I found an admin had removed messed with the update agent so although I was registering all of the required files nothing worked. My WSUS server would not send out the updates (116) that the machine needed so after searching I found this
This worked a treat Use the Stand alone installer to install the Update Agent. click here
If when you run this you get an message telling you its already installed then do the following.
Start > Run and type WindowsUpdateAgent20-x86.exe /wuforce