I have more than one PC in my office and house and after newly installing Windows Vista Home Premium I could not get my XP machine to see my Vista machine on my network or vice versa. After a lot of research on the internet, I have found how to fix the networking problem.
I can now see and access files on either the Vista machine or XP machine from either machine across the network, but I have not tried wireless access via my XP laptop yet.
The good thing is that both the firewall's of the XP and Vista machine both remain on, so there is no need to turn them off, even if you have a hardware firewall in your router.
1. Check that both the Workgroup names (not the Network names) on both of the machines are the same.
The default in Vista is WORKGROUP, although I changed mine long ago to be MSHOME, which I think was left over from XP and Windows98.
This can be changed by right clicking on 'Computer' or 'My Computer' on the desktop and then selecting Properties.
2. Make sure your Windows Vista network type is set to a Private Network.
You can modify this via the Network and Sharing Center option in the Control Panel, by clicking on Customize.
This means your computers will be discoverable on the network.
3. Make sure that the green led type lights in the Network and Sharing Center are on for File Sharing and Network Discovery.
Make sure that both computers are set up for file sharing.
4. If networking an XP machine to a Vista machine, you may need some extra Microsoft software.
This software will install the new Link Layer Topology Discovery (LLTD) onto the Win XP machine. This enables the network map in Vista to show all machines on the network. Not exactly necessary, but a nicety.
You will need to reboot your Windows XP machine, to see the changes of the software.
That's it you should now see your computers on your network. If not, try disabling the windows firewall's on both the computers to see if that is affecting anything.