AFAIK, you can't do it without a special cable: the PCs are both USB Hosts and expect to see USB clients at the other end. I haven't gone into the USB specification in that much detail, but I would not expect a direct Host->Host connection to work.
There are cable solutions available:
Google[
^] but if these are not what you are looking at then you are on your own! :laugh:
In all honesty, I wouldn't do it, personally. You almost certainly have a wired / wireless router in the form of your internet router, so I'd just hook another PC to that and do it that way.