configure vpn in adsl routers with windows xp?

Answer 1

With MOST routers you just configure windows xp for the VPN and not the router. (Its just another network connection within the network adapters) This connects one configured machine to the VPN and leaves the other machines on your system working without the VPN.

There are special circumstances which you would setup a router for a VPN if all computers connected to it are going to use the VPN. You need a router setup for the purpose, in which case you log into the router configuration and setup the tunnel first. Then your local machines are all setup with no other configuration needed.