There are three computers running Windows XP Professional on the network and two of the computers can see each other when we try to play a network game, but one computer cannot see anyone. Everyone else can see that computer. When we try to connect to that computer we are unable to establish a connection. Any help would be greatly appreciated.

On the computer that cannot see anyone. Try doing a Ping test to the other computers. To do this turn on all computers. On the two computers that will connect at the dos prompt type "ipconfig/all" and Enter. Write down the ip address of each computer. On the computer that doesn't connect at the dos propt type "ping xxx.xx.x" replace the x's with the ip address you wrote down. If your ping test is successful and not timed out. You are connected properly and most likely have a software, firewall problem

I did what you said and it timed out. Does that rule out the problem being a firewall or software issue? Any advice would greatly be appreciated. I tried pinging to two other computers that can see each other to see if it would work for both of them and it also timed out. Just a bit more info to help see if anyone can solve this problem for me. Thank you!