How can I repair my Windows 8?

To do so, follow these steps:

1. Insert the original installation DVD or USB Drive. …
2. Restart your computer.
3. Boot from the disc/USB.
4. At the Install screen, click Repair your computer or press R.
5. Click Troubleshoot.
6. Click Command Prompt.
7. Type these commands: bootrec /FixMbr bootrec /FixBoot bootrec /ScanOs bootrec /RebuildBcd.