I can do that but I need to know the exact model of the router.Is that something I can follow V E R Y step by step? Is that USB connection possible? I will only use the old Win7 pc for movies etc after support stops.?
This is another way to do it too, although doing through the router allows you to quickly undo it if need be.For a machine to get out of the local lan it must know the gateway, which is your router ip for home users. All you do is rig it so it does not have this information.
The simple way but you will have to do it every reboot is to use the command
ROUTE DELETE 0.0.0.0 mask 0.0.0.0
If you do not want to do it all the time you can assign you pc a fixed ip address in the ipv4 network settings and leave the gateway and dns blank.