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Nevermind. It seems me constantly redownloading the game multiple times confused the program. I permanently removed superfluous copies and now it seems to have downloaded fine.
adamhm: Looks like you'll need to upgrade your GPU before you can play then :(
Well, I have a laptop, so... can't do that. I plan to buy a desktop PC but a bit later, after the summer maybe. Thanks again for your help :)