Couple of things....
1. Can you ping the other computers by IP?
ping x.x.x.xip (press enter)
2. Can you ping them by computer name?
ping computername (press enter)
(*just in case you don't know how to open a command prompt to use ping, goto start/run/type cmd press enter. And dos prompt will open up)
If 1 and 2 reply 4 times with a good response then.....
Right click net neighborhood/properties
Click network Identification on the left side of the screen or from tools.
Look at the part that says workgroup... Make sure it is the exact same that they other machines are listed in.
Also the other machines need to be running in order for you to see them.. Also you will need to double click on net neighborhood and drill down until you see them. They will not just appear.
You can also open up a browser window and type in \\computername (press enter)
Any shares located on that system should appear. If it prompts you for a U/P then you will need to enter it.
Good Luck