Is there a simple way to block an outgoing IP address in Windows XP without using a firewall? I tried using the host file but without effect.
I think you're asking if you can block a specific IP i.e. 126.96.36.199
I don't have an XP machine in front of me, but I believe you can do it in the windows firewall settings. You can't do it in the hosts file as that simply resolves host names and returns a IP. I don't think there's any other way to do it.
I am not sure what you are trying to ask. If you are asking how to block anyone else on the Internet from seeing the IP address your computer is using I can tell you that this is (sorta) impossible. There is no direct equivalent to blocking "caller-ID" on the Internet.
The closest I think you could come is by using a proxy site. With a proxy site your computer connects to another server computer on the Internet and all your traffic is routed/resent through it. That way the "source IP" another computer sees is the IP address of the proxy, not of your computer.
But I've never used a service like this so I couldn't make any recommendations.