Sorry, but DigitalOcean does NOT offer Windows Server droplets.
You can only chose between Linux distros here.

I have built a guide on how to install Microsoft Windows onto your Droplet, please see here - https://www.whatuptime.com/installing-microsoft-windows-onto-digitalocean-droplet/

How to: https://teamhelps.pp.ua/top/ustanovka-windows-7-x86-na-digital-ocean/

light installation windows 7 on digitalocean: https://teamhelps.pp.ua/top/windows-na-digitalocean-za-5-minut/ install windows in 5 minutes