In theory, that's what the firewall is already doing
I suspect that what you mean is that you want to prevent that computer accessing the internet?
If so, then that's a whole different ballgame.
The best solution is to prevent ALL access to that computer except for authorised personnel - who may need internet access for updates etc. - and limit them to user accounts rather than admin accounts (except for the real admin) - you can then lock down User account access using GPO if you have Pro or Ultimate (but I have to admit that I don't know the specifics)
Win 7 ultimate. Its also on a network designed by a jackass, 5 routers all different brands jumbled together. Finding the right cable and router would be like trying to find a needle in a needle stack.
A router for each PC?? WTH did the guy think he was doing?
At this point all bets are off - you'd be better to start from scratch! (At least that way you have a chance of understanding the network)
I'd love to se a network diagram of that - NOT! (except for giggles)
You could cut that down to two, easily (assuming at least one is an 8-port router) - and have the accounts machine on an isolated network with port 80 closed off.
Is there a Server in the mix, or is it a peer network?
Finding out which router connects to the affected PC is simple, if they're wired - check the lights on the router, then unplug the problem PC and see which light goes out
I think its going to come to that, absolute pain because they keep on changing what they want done, and I was out of my depth to begin with. No server, just the machines and a DNS device they are backing up to.