Right-click on the song in iTunes and select %26quot;Show Song File%26quot;. Get information on the file (command-i). Go to Ownership %26amp; Permissions and change the drop-down menu to %26quot;Read %26amp; Write%26quot;.
If you have to do this with multiple files, the easiest way is to select the folder that they're in -- you could select your iTunes Music folder -- get info, go to ownerships %26amp; permissions, details, and use the %26quot;Apply to enclosed items%26quot; button.
If you're a Windoze user, do whatever it is that you have to do to unlock a file (change permission to read %26amp; write). Maybe in Explorer.
Hope that helps!