Yes, they should see each other. Make sure you have the following enabled:
1. Clients for Microsoft Networks
2. File and Printer sharing
They are found under Control Panel > Network Connections > Local Area Connections > Properties. You also need to give proper permissions to files/folders before other PC's can see them.
If they don't see each other after doing all these things, turn on Vista PC first, leave it for like 10 min, then turn on XP PC's and that should work out.