Automatic appending “www” to host name

I am working in Windows XP Home for the first time. I am finding that the system is appending “www” to the beginning and “.com” to the end of my typed in urls (example: http://server/app bcomes http://www.server.com/). Is this a Windows XP Home issue? How do I turn this off? I have tried going in through Internet Options on the browser to fix it, but that did not work. Thanks!