Windows update is one of the tools that I always use to ensure that the computer that I am installing or using is kept up to date with the latest service packs and hotfixes.  However I have experienced problems where Windows Update starts, but all the downloads fail to download for no apparent reason.  I think this problem is caused by the proxy server settings not being correctly read by the Windows Update tool.

In most cases where I am using Windows update, the computer is inside of a private network that has no port 80 access to the internet, therefore all access is via a proxy server that is named either by group policy or manually entered into Internet Explorer properties.

The problem seems to happen when the Automatic update feature is switched on – this of course runs before the user has logged onto the machine, therefore any user Internet settings are not used. Then when running Windows update via the Microsoft site will fail, this is because the Windows Update tool may already be running.

The solution to this problem is to switch off the Automatic Updates feature by using the applet in the control panel. Then to ensure that the update tool is not running. Use Task Manager to end the windows update tool (WUAUCLT.EXE) if it is running.

1. Open Windows Explorer and browse to C:\windows\Software Distribution.
2. Go into the C:\windows\Software Distribution\Data Store folder and delete the file named “DataStore.edb”.
3. Browse to the folder C:\windows\Software Distribution\Event Cache and delete the contents of this folder.
4. Browse to C:\windows\Software Distribution\Download and delete the contents of this folder.
5. Restart the computer and log back onto the computer.

Test that you can use the internet by browsing your favourite website. Once you have confirmed that you are able to access the internet, Use the Tools, Windows Update option of Internet Explorer. Follow the onscreen prompts- Windows Update should not function normally.

I have noticed that errors appearing in the Windows Application Event log about the DataStore.edb database being damaged after performing the above procedure.  I don't think there is anything to worry about, as the error goes away once some updates have been installed and the machine rebooted.

You can configure the automatic update tool to use a proxy server by using the command line tool called proxycfg.exe.  This will configures the WinHTTP service to use a proxy.

PROXYCFG.EXE -U

The above command configures the WinHTTP service to use proxy settings of the currently logged on user.  There are also command options that allow you to specify a proxy server to use, although the easiest is the one above.

For more information about how the Windows Update service discovers and configures a proxy server, see the Microsoft Support article - http://support.microsoft.com/?kbid=900935