Unauthorized I Tunes music not downloaded

Hello,

i just bought a new laptop n im tryin to figure out how to get ALL my music from my desktop itunes library to my latop itunes library. some of my music was downloaded from places other than itunes like limewire and it wont sync to my laptop. it keeps saying music not authorized by itunes was not synced. i authorized the computer and everything. how do i fix this? i dont want to just loose it, its like 400 songs...also, i bought new songs on my laptop itunes and i cant sync my ipod without loosing the "unauthorized songs" from my desktop library. someone please help.