I don't know if its the same for Win7, but this is how I do it for all my computers running windows xp.
First I set them to the same workgroup. Which i normally just name "Home".
Then I go to each computer and set individual folder's sharing permissions by enabling "Share this folder on the network" and "Allow network user to change files"
Then do the same to your other computers.
You should be able to see your other computers come up when you try to look for computers on the same workgroup
