you have to have shared folders on your windows PC, once you do that just go to the finder, in the top left hand corner is a network icon right above, below? the harddrive icon, click it, select your workplace from the list, pick the computer you want, hit connect, it might ask for a password, if you dont know anything about it, just try hitting enter with it blank..mine works, then select the shared folder you want from the drop down list, and it will apear as a mounted drive...if i missed anything someone add to the instructions but i think that should do it.
connecting to the mac from a PC is a little more tricky i would walk you through it but i need to be sitting at my mac and im not