What about a VLAN? But I guess VLAN can't be made by using the usual simple home equipement? If VLAN is not an option, maybe I can get another router. How would then I go about it to set a subnet with additional router only for the one PC that has the Server on it and XP as a guest so that I can experiment on it, have internet access and still leave my main network safe and intact. What would be the best practice?
I've already told you the best 2 options RRAS or a separate router and put your development LAN behind that. I have no idea why you try to do things the hard way and without the required equipment. You really just aren't listening to what people tell you. If you ask me you'd be better off learning a little more about networking (TCP/IP etc.) before you try to learn servers.