Vista / XP workgroup trouble

Trying to share files on XP machines (XP1 = Ethernet, XP2 = Wireless) with my
new Vista HP (Vis) machine through Wireless Router.
I've set :
1. LLDP Reponder and can see XP1 and XP2 from Vis (in Full Map) but cannot
browse them
2. Vis Network Discovery is on
3. All PC's File Sharing is on
4. All PC's use the same Workgroup and can all access the internet OK
5. All PC's can Ping all others
6. All PC's are 'Clients for Windows Network'
7. XP2 is visible in Vis Network hive but not browsable - error = Network
Path Was Not Found
8. Vis Public Folder Sharing is turned on
9. No difference if I turn Filewall's off

May be related... what is an IPv4 address? all other pc's just have an IP
address.

Beginning to wish I'd stuck with XP!