Itunes disc not available?

When I go to manualy up load music on I-tunes it say tat the disk is not avaliable. What does this mean an how do I fix it?

To upload music, you have to have a source selected. By default, this will be a compact disc in your cd drive. If you are trying to rip tracks from a cd onto itunes then you need to have a disc in the drive. If you have a disc in the drive, it could be copyright protection that is preventing you from ripping the tracks. If you are uploading from your hard drive then select the source location of the music.

I am confused as to why you are trying to upload to itunes. I could possibly see a use for this to add your cd's onto an ipod. If this is the case then it was my belief that you could just drag and drop music on your computer into a Library folder in your itunes program and then sync the ipod.