Network Mac to PC with USB?

No. If you want to network two computers (any combination of PC/Mac), what you need is a network. That means, a network card in each computer, a network cable in each computer, and a hub or router to connect them (alternately, you could put two network cards in one machine and connect them directly with a crossover cable, but the upgradeability of that network is low).

Once you've connected everything, then you need to get filesharing working on each machine. That can be simple or very very hard, depending on your requirements.