Shared Side Bar Help!

I have a MBP and a MB both running leopard. I also have a windows PC that I tried to set up on a network with the Macs but did quite get it working yet. Anyways, On my MBP in the sidebar only the MB shows up for shared computers. However, On the MB sidebar both the MBP shows up and also a mac address of what the computer says is a pc server. However, my pc is not even on. Does anyone know what this may be. The only thing I can think of is that it is my MBP showing up twice but why does it say it is a pc? Any way I can find out what is going on?

Thanks

So after doing some searching under my network settings (on the MBP) I have fund under my Airport preferences under the WINS tab a NetBIOS name with the MAC address and it says it is being used. What is this?