You need both to be on the same workgroup in windows(same name).Then you run the connection setup thingy and enable file sharing and printing.
What you can right click on the stuff you want to share and select share or something like that.Now with the other computer acess your other computer through 192.168.0.XX and you should see the files being shared.
You can even map a folder so that the computers on the same network can all see when they acess their drives.
You need to lock the mac adresses of the devices(ethernet or wireless) used to a fixed 192.168.0.X adress on the router so it is always acessible on the network.
I've done that only on windows XP so some steps may be different and much easier to do now.