So to solve this problem you should backup your registry, but before backuping registry keep one thing in mind that your computer should be virus free.

Procedure:-

• Ist go to Run and type regedit and hit enter, you will see registry editor( if nothing happens or pc shows some error then your pc is infected, clean it)
• Go to File and then Click Exprot. See image
  
• Then select the path to save the file and save it with the name WinRegBak.reg
• Now it’s done.

To restore Registry:-

• Double click the .Reg file that you have saved.
• Computer will ask Do you want to merge setting” click Yes
• Most of the settings will be restored by this.

An error may occur “Not all data was successfully written to the registry. Some keys are open by the system or some other processes.”