This is the Windows XP forum. There is a forum specializing in Networking issues.
I just thought I'd toss that in, not that I'm some kind of a jerk, in fact, I'll help you out.
Computers communicate with each other on a network using a Protocol. If you do not have the necessary protocol installed you will see them but they won't talk to you, because they can't.
Go Here:
Start>Control Panel>Network Connections,
Right-Click on your network card and select Properties.
Click: install, Protocol, Add, NWLink IPX/SPX/NetBIOS Compatable Transport Protocol
Click OK as needed.
Now the window having all the details about your network connections will have NWLink NetBIOS as well as NWLink IPX/SPX/NetBIOS Compatable Transport Protocol.
Try making a connection again. The other computers need communication protocols too.
Good Luck