Connecting several Slightly Complicated Network

Hi,

I hope I can explain this well enough.

We have cable - which goes into a router which goes into Computer A - Such that if Computer A is not turned on, then the internet doesn't work for any of the other computers.

Now, let computer B be one of these computers which connects to the internet via Computer A/Router.

How would I connect another computer ... Computer C INTO computer B ... such that Computer C has internet aswell?

Computer B has Dual Gigabit lan, i think it "should" be possible but I have very little idea of how to do it. I assume it's not the blue cable because I'm trying that right now (Only left over cable I had).

Assume that all computers have windows xp pro.

Hope you can help me

Thanks

What he's saying is, what kind of router do you currently have?

You can pick up a Linksys router with a built in 4 port switch for between 40-60 before any rebates. This would make your setup very simple, allow all computers internet access independently and make your life easy.