I have XP Pro and 2000 Promachines on my network and I cannot get Vista to see them let alone connect to any of their file shares. (I also have 2 Windows 98SE machines it won't connect to either, but I am mostly worried about the Pro machines.) I have Network Discovery and File Sharing turned on. Windows Firewall is disabled. I've tried to connect via UNC and IP address. Neither work. I get the error that the computer cannot be found on the network. Now I can ping these PCs successfully via their IP -and- Computer Name, so IP/Name resolution is working fine. I can also connect to them via RDP (Remote Desktop) via IP and Computer Name. Only trying to connect for file & printer sharing does not work. I am using Vista RC1 Build 5728.

Try to delete previous configuration of Network and re-do the Wizard of Connect to a network. It should work. Good luck