When booting up after Windows failed to start, you should automatically see an option called Launch Startup Repair. However, if you don’t see it, highlight Windows 7 and then hit F8 on your keyboard for advanced boot options. For more information on this, click here
1. Step Select ‘Launch Startup Repair (recommended).
2. Step Next, Click on the Next button.
3. Step Next, Select Windows 7 and click on the Next button. Then follow the wizard to fix any startup errors
Opening the safe mode and using the Windows File Checker may help you in some cases