Can I completely remove the internet or prevent someone from modifying IE Options?

So I’m trying to disable the internet access on a computer at work. I still want it to connect to the lan so I can’t just disable the ethernet card. I’ve uninstalled IE but if you type a URL in the folder address bar, you can still load websites. So, right now I have it pointing the internet at a fake proxy. The only problem with this is that any person could go and turn off the fake proxy and they’d have internet. So I’ve got to ask, is there anyway to prevent a person from changing Internet Options in IE 7.0?
Or, in the broader case, can I stop them from getting onto the internet another way?

Why not block the PC’s IP address at your router? Or you could assign it a non-routable IP address.

You can go into IE and set a password in the content adviser thing. I don’t currently have the latest version of IE installed so I can’t tell you how to get there, but that’s what we do at work when we don’t want people browsing the internet. That’s probably the simplest way of doing it, but it’s rendered useless if someone just installs Firefox (or puts Firefox portable on a thumb drive). Do this if your target user(s) aren’t very tech savvy.

If they are, your best bet would be to use a firewall to limit outgoing connections to only the addresses the computer has to connect to.

If this is on a domain or Active Directory, you can set a policy to lock down the user’s ability to change settings. There’s plenty of documentation on Microsoft’s website - look up ‘policies and profiles’ and ‘group policies’.

If it’s just a single machine, you can still set Group Policies: Start | Run | GPEdit.Msc.

Be careful!

You could remove the default gateway entry from their routing table.