Have trouble installing updates from Windows Update? Check out the Windows Update Reset Tool written by the Fix-It Team at Microsoft. This tool resolves most of the Windows Update and Automatic Update issues by resetting the Windows Update configuration.
This tool automates the most common fixes (including DLL registration) to issues with the Windows Update site. This Fix it Solution has two modes Default and Agressive. You should run the Fix it solution in Default mode and determine if it resolves your problem with Windows Update before running it in Agressive mode.
Download Windows Update Reset (Fix It) Tool from Microsoft.
Editor’s Note: My friend and fellow MVP Bill Castner lists out the manual troubleshooting steps to fix WU/AU problems. You may like to check out the above link as well.