When I was using windows, I could disconnect the internet on my dad’s computer from my computer (for instance if it was playing up and I wanted to restart it which often resolved the issue) and didn’t need to go all the way downstairs to do it.
Is there any way I can get it to be possible to do that from Linux?
There are a couple of ways you could do it. If it’s running linux, You could connect to his machine remotely over SSH, and shut it down, or firewall off the internet, or delete his default system network gateway… Or you could use NX machine, or VNC, to connect via a GUI.
Or, if it’s running windows, you should be able to use RDP to logon to it, assuming it’s running one of the more expensive versions of windows (i.e. not home personal)
… or you could spend £20 on a router and never have the problem in the first place … 
Well I would also need to spend however much on getting a non usb modem, extort the details of our isp from my dad etc etc…
And yeah, it is not one of the expensive windows. Just xp home.
No, the router would replace your USB modem … both / all PC’s could connect directly to the router … Dad’s PC no longer become a point of failure for you, and the router will be way quicker at IP than your Dad’s PC, so all of a sudden your connection will get much faster. On older PC’s between 2x and 4x (!)
I would recommend that as well… I’ve not used a USB modem… well, ever really. Dad used to use one, we setup a spare machine with shorewall / ipcop (turn spare machine into a router), but a dedicated one is better.
You’d need to look into running a VNC server on the desktop machine, and then you’ll be able to use remote desktop (Applications > internet on ubuntu) to connect to it.
If you got a linksys one, you could put linux on it anyway:
http://openwrt.org/
You guys overestimate the control I have over this :(.
Ok, USB ADSL modems are for people who don’t know any better, maybe that’s a little blunt but it’s the truth … It’s what ISP’s give away free because it’s the cheapest and nastiest solution going AND it spares their bandwidth by slowing down your rate of access. Not to mention the flakey drivers that are a potential security risk that always slow your PC down if not contribute to it hanging. Or , you could point out that shifting to a router will speed up his machine by at least a factor of two compared to times when you are accessing the Internet via his machine … if £20 is too much, don’t eat for a few days and save up - the difference will be worth it!
But how do I get the password for the isp…
When you sign up for a service, they’ll send you a username /password, this needs to be entered into your PC to make the modem work. If it’s been lost, you can always call the ISP and ask for some direction …
Well Mark helped me out on this one.
But I didn’t sign up to any services, I don’t think my dad would have forgotten the password.