For your windows PCs you will have to enable "Client for Windows Netwoeks" (Vista) in the NIC card properties to get the browsing working. I think in XP its NetBIOS or something like it.
What do you mean by the desktop1 network? The desktop server's IP address or the base network address for the entire network? You may have DNS configured incorrectly too, which is why you are getting referred to the Internet when you are trying to ping a local machine.