Since you already purchased the game. You can simply download the game using another PC.
Keep us posted.
What a ludicrous post.. with that level of support I don't really know why I'm bothering to add to this.
I've also bought FH3 on pc but with 1.8mb internet it'll take about 9-10 nights to download. Planned to send a USB stick to a friend for him to copy his game data - paste it over the top of my own windowsapps folder, then resume the download in my windows store.
Steam/Origin as others have said would pick this up as data being present and carry on with the installation.
Does this mean that windows will just ignore this entirely and carrying on trying to download all 50gb? What an absolute waste of time this game is proving to be.. let alone all the performance issues I'll no doubt face if it ever is installed!
Maybe I should just get a refund now...