Windows ISO download links

This is the list of some of the legal Windows ISOs. All of them are final releases, and they are mostly hosted on Microsoft, but some of them are from other sites (not including torrents or other illegal methods of download)

You WILL require a product key, and ANY ISOs that come preactivated WON'T be listed here.

If you don't have the product key for the OS you want, DO NOT install it on your actual PC. Use a VM to do so, as it will expire in a few days or weeks.

I CANNOT guarantee that these are all legal. Use at your own risk.

HeiDoc's Windows ISO Downloader
The Windows ISO Downloader is the best method to download Windows ISOs legally after Microsoft shut down the Tech Bench page for downloading them in 2016. It's free and easy to use. Includes some editions of Windows 7, 8.1, and recent releases of Windows 10. Available SKUs:

Windows 7

 * Home Premium SP1
 * Professional SP1
 * Professional SP1 Upgrade
 * Home Premium SP1 OEM
 * Professional SP1 OEM
 * Ultimate SP1 OEM

Windows 8.1

 * Windows 8.1/8.1 Pro (combined in a single ISO image)
 * Windows 8.1 Single Language
 * Pro LE
 * N/K/KN editions

Windows 10

 * Most of current releases

Windows XP derivatives
THIS DOES NOT INCLUDE THE ACTUAL WINDOWS XP, since it's still illegal as of today. However, there are some alternatives you could try.
 * Windows Fundamentals for Legacy PCs (based off Windows XP embedded)
 * Install tutorial by mjd7999 (yes, the download link was taken from the video's description)
 * Overview video by MajorSky17
 * Service Pack 3 for WinFLP (this OS only has SP2 installed)
 * Windows Embedded POSReady 2009 Evaluation (Windows XP variant that's supported until April 2019)
 * Install tutorial by mjd7999
 * Windows Embedded Standard 2009 Evaluation