Installing Windows 7 without the disc:

https://www.pcworld.com/article/248995/how-to-install-windows-7-without-the-disc.html


Windows 10, 8.1 and 7 ISOs from Microsoft:

https://www.microsoft.com/en-us/software-download/windows7

https://www.howtogeek.com/186775/how-to-download-windows-7-8-and-8.1-installation-media-legally/


Creating a Windows 7 Repair Disc and accessing command prompt:

https://support.microsoft.com/en-us/help/17423/windows-7-create-system-repair-disc

https://www.bleepingcomputer.com/tutorials/windows-7-recovery-environment-command-prompt/


Recover Windows Product Key from Registry:

http://www.prime-expert.com/articles/a10/recover-windows-product-key-from-registry.php