Cannot find computers on network

I am having a home network. I have added 2 new pcs and they are both on Vista. The original home-office computer is still on XP. Previously I was able to see my home-office computer, the one on XP, but for some reason, from the home-office computer, I am not able to see any other computers. If I am going to My Network Places and click "View Workgroup Computers" then I am getting an error message that says "Workgroup is not accessible. You might not have permission to use this network resource. Contact the administrator to find out if you have access permissions. The network path was not found." Can anyone tell me how to solve this issue?

Are the Vista computers are able to see each other? I think they maybe not. Are you having any shared resources on your new Vista computers, that is, shared folders or printers with appropriate permissions? Is the file and printer sharing turned on for the Vista machines? After that you must get a logon window for the Vista when you try to connect to the Vista box from your XP, that will only pop up the first time you connect.

This behavior may occur if all the following conditions are true:

1. NetBIOS over TCP/IP is not turned on (enabled) on one or more computers in the workgroup.
2. The Computer Browser service is not started or is turned off on one or more computers in the workgroup.

So, to solve this issue, follow the steps given here - http://support.microsoft.com/kb/318030