Automatic Repair on Windows 8

If you want to access and run Automatic Repair manually, you need to open the Charms Bar. From the Windows 8 charms bar, click on Settings > Change PC Settings > General.
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Select Advanced Startup and Restart your PC. This will let you start Windows from an external device, change Windows startup settings or restore Windows from a Factory image. On restart, you will see the following screen.
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From the WinRE screen, select Troubleshoot > Advanced options.
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Under Advanced options, select Automatic Repair.
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You will be asked to select the User Account to continue. Do so and continue. If asked, enter your password too and click on Continue.
Windows 8 Automatic Repair will now commence and try to identify and resolve the problem. This process may take some time and your system may even boot. Once the process completes successfully, you will see a message to this effect.
If Automatic repair fails, and you get an error message Automatic Repair couldn’t repair your PC, you may check the log file  at C:\Windows\System32\Logfiles\Srt\SrtTrail.txt. You may also want to check this post on Windows 8 fails to boot; Automatic Repair, Refresh, Reset PC also fail.