I have a problem with getting my music files which are in the Itunes folder under music and I can see all of them but can not transfer them to my Ipod. When I try I get something like file name can't be found do you want me to search for it?

I uploaded music from Limewire to Itunes and now when I open Itunes and try to move my music in my music folder to the Ipod icon I get the can't transfer icon, you know the one that looks like a circle with a line through it.

I must be doing something wrong to get the Limewire music files into Itunes so I can upload to my Ipod.