If I'm in the wrong forum, I apologize.

I keep getting a red triangle in the upper right hand corner of the screen.
Clicking on it says there is an upgrade problem.
Clicking on 'Check for updates' gives the following error.

W:Failed to fetch cdrom://Ubuntu 12.04.1 LTS _Precise Pangolin_ - Release i386 (20120817.3)/dists/precise/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 12.04.1 LTS _Precise Pangolin_ - Release i386 (20120817.3)/dists/precise/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.

How do I solve this?
TIA

dlw