How To Remove Name From Network

Just installed windows 7. On setup I gave the computer a name. e.g. My-PC "my-PC" was part of a homegroup which I thought I had to set up.I already had a network called homenet that I thought this might allow me to join. Instead, homegroup became a new network. I removed the home group and all was OK.Under "network" in windows explorer, all XP computers, NAS box, and attched printers showed up, along with the new win7 pc, "My-pc" so all seems to be OK.I did not like "My-PC" as the name of the win 7 computer so I renamed it. e.g. "My-New-PC".I rebooted and when the network list came up, both "My-PC" and "My-New-PC" BOTH showed up in the list, but "My-PC" in not accessible.Since it no longer exists withthat name, how can I remove the name from the network? So to summarizing this I have a renamed computer where the old name AND the new name for the same computer exisits on the network, but the old name is unaccessible and I want to remove it fromthe network(list).