1. Insert your Windows Vista or 7 discs in your computer drive and restart your computer.
2. Hold down the 'F8' key on your keyboard while the computer boots up. This will open the 'Advance boot options' screen.

3. Select 'Repair my computer' and press 'Enter.'
4. Select 'Startup Repair' from the list of options and click 'Next.' Startup repair will scan your computer for corrupted and damage files, repair them and boot up your computer.