I have to uninstall ROS Indigo because I had many troubles when I tried to use roslaunch, but when I wanted to install again and runs

$ sudo apt-get update

Terminal displays the next error messages

    W: Failed to fetch cdrom://Ubuntu 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)/dists/trusty/main/binary-amd64/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 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)/dists/trusty/restricted/binary-amd64/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 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)/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 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)/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

W: Failed to fetch http://packages.cor-lab.de/ubuntu/dists/utopic/main/binary-amd64/Packages  404  Not Found [IP: 129.70.142.22 80]

W: Failed to fetch http://packages.cor-lab.de/ubuntu/dists/utopic/main/binary-i386/Packages  404  Not Found [IP: 129.70.142.22 80]

E: Some index files failed to download. They have been ignored, or old ones used instead.