Don't worry, you're not the first and certainly not the last. These zip, rar, and 7z are archive files. What they do is "compress" the files inside them to make them smaller. This means faster downloads for you and less bandwidth used for us. But you can't just use these files as they are. You have to first uncompress them to get the files that you want. Windows has a built in uncompresser that can handle most zip files, but you'll need something else to get those files from those rar's and 7z's. The most common programs to do this are WinZip, WinRAR, and 7-Zip (free). You might also wonder "what's the difference?" Basically, zip, rar, and 7z use different algorithms, or methods, for compressing the files. Some give better results then others in different cases, so that's why you'll see different ones. Personally, I like 7z because it's open source and gives good results, but rar is another favorite around here too. All of the latest versions of WinZip, WinRAR, and 7-Zip will open any of the different formats, so just pick the one that you like the best.