Can anyone shed any light on this?

I am running vista and in the network and sharing centre it is showing multiple networks.

1st one is network (private network)
access local and internet
connection local area connection

2nd one is unidentified network (public network)
access local and internet
connection local area connection

I only have my pc wired up to my router so why would I have multiple networks? (xbox is set up on wireless but not switched on and still multiple networks are showing)