What did you download the game with? Cuz sometimes if you use google chrome it can corrupt the files and not work. If that's the case, try to download it again using Internet Explorer, or possibly even torrent it if you have the capability to.
If that's not the case, it might the the extracting process itself that you're having trouble with. I, personally, favor the use of Winrar. It's fairly easy to use, even though Windows 7 comes with a basic extractor, it sometimes doesn't work for bigger files like EPW.
