The IP you listed is likely a computer on your internal network.
There is a simple command prompt command that allows you to find computer name via IP (you will have to be on the network of that machine).
There is no good way of finding a remote pc's subnet mask though.
The best you can do is do pings up the IP list until it stops (assuming you are on the same subnet). Now depending on how wide the subnet is, this could be thousands to millions.
Now where did you get the 255.255.255.0 from?