Zquinty

I can't seem to download ANYTHING!!! I managed to download one mod, but then every mod I attempted to download after that didn't work - My computer download the files fine, but they are saved as ".7z" files, which my comp wont recognize. I tried adding ".esp" and other extentions at the end of the filename, but this does nothing for me. The downloaded files I get are essentially blank and unreadable. How do I remedy this?