I found this site on Microsoft's Help and Support Page for Windows Vista. It gives instructions on how to fix Windows Update issues by error code. The error code can be found by going to start>programs>windows update>view update history. Once you get there you will see a list of the updates that have either failed to install or successfully installed. To find the error code you can double-click on the failed update and a window will pop-up with the installation info along with the error code. I have attached a screenshot to show you how. Once you find the error code you can go to Windows error codes
and find the error code. Once you have found the error code, you can double-click on it and it will redirect you to a page with detailed instructions on how to fix the problem. Hope this helps.