You can get Red Alert at a lot of online vendors. However, my and my pals have been using the Origin version and it has worked great on Windows 7, 8 and 10. You can get it and all Command and Conquer games from Origin, here:
https://www.origin.com/en-us/store/buy/c-c-the-ultimate-collection/pc-download/bundle/ultimate-collection
You can also play the open source version for free here:
http://www.openra.net/
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