Can't Get PC Game to Start

I have never had trouble downloading PC games on my computer before. Now when I put a disk into my computer, the computer doesn't even recognize that it has a disk in it. Even when I go manually into the computer and click on the Disk drive, it just tells me to put in a disk- when there's a disk already sitting in it. 

I'm trying to download a PC game and I think my Norton Antivirus is preventing the computer from recognizing it. I was able to download it on another computer just fine so it's not the disk. And the computer giving me trouble was able to rip music from a CD so it's not the disk drive either.