Networking; This is how I tranferred my digital tracks from my PC to my Mac. Get a network cable and connect your computers. You don't even need a "crossover cable", your mac can use a regular ethernet cable as a crossover cable between any other computer. Enable file sharing on both computers. Use the Powerbook to establish the network connection. Open iTunes and choose File>Add (NOT import) and then browse to the folder with your music on your PC.

Easy and fast.