Ok, all you need to do is hook the Mac and the PC together using any type of CAT 5 cable.
Then go into the Mac's System Preferences -> Sharing, check off Window sharing, at which point it should give you the address that you can plug into the IE on the Windows computer to go into the Mac. The IP address it should be getting is something like 169.xxx.xxx.xxx. When connecting, give it some time, it can take a few moments to work.
If you need to get into the PC, you also need the IP address of the PC this time. So get your nic card IP Address, which can be done by Right clicking Network Nieghberhood, Properties, then double click on the Nic connection and it should tell you the IP. Another way to get the IP on all Windows computer is to click Start, Run, type in "cmd" without quotes and hit enter. Then "ipconfig /all" without quotes in the dos prompt, and it should give you all you need to know about the network cards. Once you have the IP, click on the Finder face in the dock on the Mac, Click go in the menu at the top, Then "Connect to Server..." (which is also cmd + K as a short cut). At which point, put in your Windows IP address and Connect.
Note, don't have either the PC or the Mac hooked into any other connection, since it will default to using that other connection, instead of the one between them. So if your Mac or PC has wireless, turn it off.
That was the quickest way I could explain it, and it might be a little off in spots, but that is the basic way of doing it either way.
