OK I just tried to purchase it and install it again. Still no success. Also the first time I purchased I was given a Steam Key, but someone quickly stole my steam account and I was unable to use it. I tried deleting all of the files from the first purchase and installing it again with the second purchase. No success. I'm going to ask you for my money back if you cannot solve this for me. I was installing the windows version and I do indeed have a 64 bit system. There was plenty of free disc space on my computer so that was not the problem. Please fix this for me or reverse my charges.