Somebody please help!!!

i have just discovered the wonders of Limewire and have successfuly manages to download all the software, and i can also download tunes into my library, however i am unable to play them or put them into itunes as i keep getting a message that say it can't recognise the file type (mp3)

i have a G5 imac which runs with Tiger and OSX v1.4

Can anybody help please, any suggestions wuld be very much appreciated