Can you provide some more information.
- Brand and details of laptop
- Are you using an operating system that came installed with the laptop?
- What Windows reinstall or Factory restore options do you have
- Provide a screenshot from Windows Disk Management of both your laptop and external HDD connected.
To provide the screenshot
- Type "disk management" bottom left search box
- follow this tutorial to capture and upload Screenshots and Files - Upload and Post in Seven Forums
It's evening here so I'll look tomorrow if someone else doesn't before I do.