The document discusses diagnostic computer software and programs. It explains that most users do not realize they have an operating system problem until they receive an error message. Before this, the computer may slow down or input devices may malfunction. Diagnostic software can identify issues and repair errors through safe mode. It allows repairs while limiting normal software functions. The system restore option also allows restoring the computer to an earlier state. If diagnostic software fails, reinstalling the operating system may be necessary. Regular backups can prevent data loss.