how does one reset the file exchange? please help
 

I have been downloading music to my ibook via limewire, and it has been saving it to itunes automatically, but after installing quicktime 5.0, after d-loading a song it shows up in Q-time, I have read post about reseting the file exchange, any directions on how to actually do it? I am new to this computer stuff. MAc ibook, os9.1