Unzipping files downloaded from the Cox Cloud server

Hi, I recently had to replace my hard drive. I had previously uploaded my pictures and documents to the Cox Cloud server, so I tried to restore them by download. The files downloaded as compressed (zip) files, and when I tried to open them, I got an error window that said that windows can't open them, as they are Compressed (zip) files and are invalid. I searched windows help and forums, but they just said to drag and drop them where you want them and open them. I tried dragging and dropping them to the desktop (where they are now), but when I click to open them, I get the same error message. Any advice out there would be appreciated. Thanks in advance.