Tonye:
I would asume it's pretty ease using the ethernet connection. Just directly the mac to pc with an ethernet cable (RJ45), and enable file sharing on both machines. Easch will sense the other as a server. You should be able to transfer file back and forth quickly and easily.
The firewire is a another story. You can connect them using a firewire cable, but I'm not sure how the pc will react to firewire disk mode. Try booting the mac in firewire mode and hoping it senses the pc as a disk and then just drag and drop files. The mac file can't be read by the pc but you should be able to drag and drop them, but I'm not sure if the pc file system will even recognise them. The pc files will be recognised on the mac, but you can't run exe files, just open docs. Anyway the firewire transfering method would be very slow in contrast to the ethernet way.
Hope this helps