changing scope of port 1433

I am trying to limit the scope of port 1433
for sql server on an xpsp2 box. when I type in
a specific I.P. and subnet for the server on
the client machine (10.10.0.xxx)and close the
window, when I reopen it the I.P. has changed
to 10.10.0.0. the subnet seems to be retained.
Does anyone know why this is, and how to get
around it. Any help would be appreciated.
Microsoft has much information on how to
change the scope, but precious little on what
to do if it doesn’t work.