Itunes wont sync. my music. . . please help!

my dad recently bought a new computer and i downloaded my itunes onto it. before on my old computer i had an itunes with like 200 songs, everytime i try to download music onto my ipod, a message pops up saying that if i transfer the new songs onto my ipod all of my old songs will be deleted, so i let it delete them, but i made sure and went on limewire first and put my songs on there so i would be able to re-download them. but when i tried to download them again, it said it was syncing my ipod but no music showed up. . . i am so confused can someone please help me?