First pull up a command line (start>run>cmd) and try to ping one machine from the other to make sure they can see them. On the other machine's command line type ipconfig to get the ip address from the other machine and then type ping <ipadress>. If that works, you can reach the other machine.

Share something on the other machine (the whole C drive if that's waht you need) and go to the other machine open my computer and go to my network places. If nothing shows up in there, open up the run box and in the Open: field type \\<name of computer>. Remember, those are backslashes, not forward slashes like you would use in a http://. It should pop up assuming it can find it.