I have a dell Inspiron 7537 which is more than 7 years old and used as a secondary laptop. It was working fine until now but it's hard drive has died yesterday. I have ordered online a replacement Segate SSD drive to install.

My questions is - I did not receive any Windows CD with my purchase of Inspiron 7537. The laptop had Windows 8 installed which I did not upgrade to Windows 10. I can download the Windows ISO from Microsoft Website and put it in a disc and install but I would need an activation key. I called Dell and they were not able to provide a key. I am sure as a part of laptop purchase I purchase a license for windows as well. How can I have Windows 8 or higher activated on the laptop? 

Thanks for your help.