Considering the number of updates that are pushed out through Windows Update every year, this service is quite reliable. Nevertheless, sometimes Windows Update does not work properly. Due to the complexity of a modern operating system, many possible causes for Windows Update errors exist. In this article, I list the most common troubleshooting tips related to Windows Update errors. Since the Windows Update Agent is the client for the Windows Server Update Services (WSUS), these tips can also be used if you are working with WSUS to deploy updates in your network.
Download the Windows Update Agent (WUA)
As a Windows component, the Windows Update Agent (WUA) is also updated through Windows Update. But if Windows Update errors occur, you should check if you really have the latest version. You can determine the WUA version by checking the properties of wuaueng.dll in %SystemRoot%\system32\. As of this writing, the current file version is 7.5.7601.17514 for Windows 7 and 7.4.7600.226 for Windows Vista and Windows XP. If you don’t have the latest WUA version, you can download the Windows Update Agent here and then install it manually. Even if your Windows Update Agent is up to date, you could check out whether reinstalling WUA solves your problem.
Reset Windows Update Agent components
Reinstalling the WUA is sometimes not possible because Windows recognizes that the latest version is already installed. In this case, resetting the WUA components can help with some Windows Update errors. Resetting Windows Updates components means registering the Background Intelligent Transfer Service (BITS) files and a few other things. The whole procedure is a bit long-winded. The fastest way is to just click the "Fix it" link (preferably in Internet Explorer) on this support page. Note that Windows 7 is not listed in the Applies To section on the page. However, when I ran Fix-it-MSI, it appeared to work properly on Windows 7 as well. The Fix-it wizard will ask if you want to run the aggressive options. Aggression is always the last resort in problem solving, so you had better skip this option at your first try.
Install Windows updates manually
Occasionally, particular Windows updates fail to install. It can be quite annoying if the same update is offered again and again, especially when reboots are required. In those cases, you can try installing the update manually. First, you have to find out the KB number of the update with the Windows Update user interface (type Windows Update in Start Search in Vista and Windows 7, or press F1 on the Windows XP desktop). Then, you have to search the corresponding download page in Microsoft’s Download Center; or, just google the KB article, which is often faster. If you can’t find a download page for the update, you can try the WSUS Offline Update Generator.
Windows updates are usually MSU or EXE files, which means that you can just double-click the files to install the update. If you want to run the update on multiple machines in a batch a file, you can also use the wusa command (wusa.exe file-name.msu) In some cases, it can also be helpful to extract the MSU file first with the expand command and then install the Windows update package with Package Manager (pkgmgr.exe). More information about this procedure can be found here, and all Package Manager options are listed here.
Install the Windows update in Safe Mode
If an update is still stubborn, you can try booting up in Safe Mode (press F8 before Windows starts) and install the update again. If an application is interfering with the update’s setup program, then this could solve your Windows Update problem. However, when I tried installing a Windows update in Safe Mode the Windows Update Standalone Installer failed with the error message: Installer encountered an error: 0×80080005. Since this Microsoft KB article also recommends installing updates in Safe Mode, this might have been an issue with the update I tried. Note that starting the Windows Installer service in SafeMode, didn’t solve the problem. Another option is to install the update with Package Manager (see solution above). This should also work in Safe Mode.
Remove malware that blocks Windows updates
One of the reasons why an update often can’t be installed is because malware is blocking it. Usually, this update closes a security hole that the malware requires. In this case, you can try getting the latest signatures for your antivirus program. If this doesn’t help, you can boot up theTrinity Rescue Kit or UBCD4Win and run an antivirus program from there to get rid of the malware.
Fuente: Michael Pietroforte