The windows utility will only show you all connections on the local machine. So, you might have a wireless connection on a 192.168.*.* subnet, and a lan connection on another subnet, etc. It does not show you the IP Address of another computer connected to the network, unless you ask some name lookup service, for eg DNS to give you the IP address of a target computer.
As someone suggested above, you need to talk to your wireless router, and get the information. Or, if you know the hostname of the other laptop, you can try to lookup the address provided the router does DNS registrations for all hosts on it's network.
hope that helps.
feroze
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