copying files denied: the file name was invalid or too long

hi there i keep getting the above error message pop up when i try to consolidate my library. basically im trying to move my music from its current location to a new computer via external hard drive following the itunes directions but this error message is preventing me from continuing.

any ideas on what to do??? i have looked at other solutions on here and it tells you to go through files in list order but mine appear to be organised into folders.

any help would be appreciated thank you!