The automatic repair tool in Windows 8 can be used to resolve common issues that can cause Windows 8 not to start up properly. In the event that Windows 8 cannot start the Automatic Repair tool will start automatically. Once started it will scan various things such as system files and settings. If it detects any problems it will automatically attempt to fix them.
You can also access the Windows Automatic Repair tool manually.
Using the Automatic Repair tool in Windows 8
To access the "Automatic Repair" tool go the the Windows 8 Start Menu and type "Advanced".
Click on the "Settings" category.
Click on "Advanced startup options" to see the General PC Settings screen.
Scroll down and click on "Restart now" under the "Advanced startup" heading.
Click on "Restart now"
Windows 8 will now restart into the Advanced Startup options menu.
Once in the Advanced Startup menu click on "Troubleshoot"
Click on "Advanced options"
Click on "Automatic Repair".
Your PC will now restart and you will see a login screen. Select a user account that has administrator privileges.
Windows 8 will now attempt to diagnose any problems. Be aware that the automatic repair process can take quite a while to run. During the process your PC may restart, this is nothing to worry about.
Once the process is complete Windows will tell if it has successfully repaired any issues. If it was unable to repair any problems you will be given the option to shutdown or use other tools to try and rectify the fault.