You need to change the Network Name on all Powerline adapters to something other than default "HomePlug".

You can do this by connecting each adapter in turn to your PC and changing each one individually, or by entering the password from each unit and changing the Network Name remotely via the "set all devices network name" button in the utility.

Also Windows will remember the name of Network Computers for a time, even after they are disconnected. If you still see your neighbours computer after changing Homeplug Network Name, that's probably all it is. Just a phantom entry. It will probably go next time you reboot (computer + router) or flush the dns cache.

Thx, I had changed the network name. I've rebooted all the PCs and the router. It seems to have disappeared. Will keep an eye to see if it comes back.

Would be better if the kits shipped with a random generated network name, and then instruct users how to change it when adding further devices to a home network.