I think you are being a little naïve. That web sit is just the root. If you click on the Netblock owner (National Institutes of Health) link you'll see all the websites HHS runs. Not only are there are many MS servers there are also many Linux and Solaris as well. http://toolbar.netcraft.com/netblock?q=NIHNET-2,13 7.187.0.0,137.187.255.255