Microsoft Windows Support Number, You must have the first Microsoft Windows 7VistaXP disc (from Dell) or Dell system restore disc for reinstalling.
https://www.youtube.com/watch?v=RhkVCSkF4fo&t=2s
https://youtu.be/Y07rTXyvx-I
Microsoft Helpline Number +1-800-201-4243 (toll-free) Are you searching for Microsoft assistance? If you are facing issues while using Microsoft products.