Same problem here. I have two Vista computers, and one XP Pro computer, on a lan. The Vista computers can see each other and share files fine between them, however neither of the Vista computers can access shared folders on the XP computer. The XP computer shows up in Network on the Vista computers. The XP computer can access shared folders on the two Vista boxes after authenticating. I installed the LLTD protocol on the XP box, to no avail. Workgroup name is same across all computers. I unset Simple File Sharing on the XP box and opened up permissions so Everyone has read and change access, no change. Pinging the XP box's IP address from Vista times out. On the Vista computers, Network Discovery and File Sharing are turned on. This all worked transparently when there were only XP computers on the lan.

I am having the same problem from a Vista laptop trying to view files/printer on a XP workgroup. In the Vista network window, I don't see the XP PC. I have enabled Network Discovery and File Sharing on the Vista laptop and I have set it as a private network. I can successfully ping the XP PC from the Vista laptop, though. Any help would be greatly appreciated.

http://nitecruzr.blogspot.com/2006/12/windows-xp-and-vista-on-lan-together.html might help you. Not me. I tried enabling NetBT on both network adapters in case the wireless router was having an effect, but this did nothing. Another note, when I try and connect by simply typing \\computername results in Vista coming back with the error: "A device attached to the system is not functioning."