You fail to identify the OS, but it appears to be a Windows OS since you mention DOS. I believe that even if you use the DOS "route /delete" command in DOS, if the Gateway is configured in the GUI, it will re-appear after a reboot.
The obvious answer is to remove administrator privileges from this user's account (it should be removed from everyone's account). I believe that this can be handled through a group policy setting if you are Windows XP on an Active Directory Domain.
But it sounds as if you are a small network, without much in the way of centralized control. If that is the case, I would be more likely to do something like defining a different route on the gateway for that subnet, so that packets from the Internet to this user's machine cannot be routed correctly.
Or I might choose to do MAC address filtering, and only allow the MAC addresses that I wished to have access to the Internet to get through.
A lot depends on what equipment you have at hand, how big the network is (what has to be done to reconfigure) and how much you are willing to invest in filtering technology.
pansophic
