Can I change the platforms I can build to without re-downloading Unity?

I recently made a game, and I wanted to share it with some of my friends. However, some of them have Windows machines and I stupidly forgot to install that build option when I first installed Unity. Is there a way for me to add that build option without re-downloading all of Unity?

Thanks!

The Unity download (for newer versions) is just a downloader component (so, it’s small). Download that and run it. There, you can choose which options you want to download.