Not sure if the article really covers this: Vista insists that at least one user account on itself and the remote machine have a password before it will share.
I wrote the following for Windows, but think you can use it for MAC with some changes:
a. "Command prompt" window is probably called Terminal or Console in MAC.
b. "ipconfig /all" is ifconfig -a in MAC
c. in MAC the ping command may go "forever" until you hit the CTRL + c key combination. You can also do ping -c4 to do only 4. I'm making these two guesses because MAC is based on Unix.
To open a Command Window: Start - Run – cmd (command in 98SE) – OK
(if Run not on Vista’s or 7’s Start menu, just type cmd in the Search box)
To determine a computer's IP address: open a Command Window and type
ipconfig
Now for some troubleshooting:
1. On each PC open a Command window and type
ping IPofOther (where IPofOther is the IP address of the other PC)
Do you get Replies, or do you get packets lost?
If you got Replies,
2. Do the same ping except use the Computer Name of the other computer:
ping NameOfOtherPC
Replies or lost packets?
If you got Replies to either or both,
3. Then
Start - Run - \\IPofOther - OK
With luck after about a minute you should get an explorer window showing the other PC's shares. If not, what is the error message?