I have a warning triangle on the top of my screen. When I click on it, it says that my update information is outdated. When I type sudo apt-get update && sudo apt-get upgrade into a terminal, I get this message: W: Failed to fetch cdrom://Ubuntu 14.04 LTS _Trusty Tahr_ - Release i386 (20140417)/dists/trusty/main/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 14.04 LTS _Trusty Tahr_ - Release i386 (20140417)/dists/trusty/restricted/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs E: Some index files failed to download. They have been ignored, or old ones used instead. Any ideas?