If you discovered that one or several system files are corrupted or deleted, there is a way to restore them from Windows installation CD, DVD or ISO image.Instructions for Windows 10, 8, 7 and Vista1. Download and install the latest version of 7-zip. You may need to download one of the betas, because the latest stable release of 7-zip might be too ancient to open WIM files from the newest versions of Windows.
2. Open the root of the installation media.
3. Open the Sources folder and find the file named install.wim.
4. Right-click the install.wim file, then point to 7-zip, and then click Open archive.
5 (optional). If you see one or more directories named from 1 to 6, then open the folder that has the highest number in its name.
6. Open the folder that contains the file you want to restore, right-click the necessary file and click Copy to.
7. When the Copy window appears select the folder on your hard drive where the file should be placed and click OK.

I've had this issue with a couple computers (my own!)  For some reason the Windows Update services is turned off.  To turn this service on:
​1. Press Win+R keys together to launch RUN dialog box. Type services.msc in the textbox and press Enter to open services manager.
​2. Scroll down to Windows Update and double click.  Change the Startup type to Automatic.
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