Here is a list of different problems you might run into when updating windows:
Error: Windows update can not currently check for updates, because the service is not currently running , try restarting your computer
To solve this issue, try the following steps, one by one and try the windows update after each step.
1) Reboot your computer
2) Make sure the service Windows Update is started and Startup Type is set to "Automatic (Delayed Start)".
3) Stop and restart the serviceWindows Update
4) Stop the service Windows Update, rename or delete the folder C:\Windows\SoftwareDistribution, restart the serviceWindows Update
Error: code 8024200d when updating a file
1) Note down the name of the update that is causing the problem (e.g. Security Update for Windows 7 (KB2667402)
2) Open Control Panel - Program & Features
3) Choose "Uninstall an update"
4) Search for the update that is causing the problem in the list
5) Press "Uninstall"
6) Run Windows Update again
Windows Update dialogue shows no text but#elementModuleHeaderText# instead
This is a known Windows problem. Install and run the Microsoft Fixit from this MS knowledgebase: http://support.microsoft.com/kb/KB971058