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I recently had to reinstall WIN 10. After doing so I found out that my Diablo III game files (all of it) are gone. Disappeared. Is there any way I can re-install the game/access my account without having to repurchase?
Yes. You need to reinstall the Blizzard app located Here. Once you have your Blizzard app installed, login and click the Diablo III tab you will see the big blue button that says: Install -> The game will install.