Router Router Router

You need a router. Thats why. Switches and hubs don't understand IP addresses, so when DSL comes in, you get one IP address and that's it. Which means only one of your computers will get the IP to use on the internet. An IP address is like a mailing address for the information being sent over the internet, if you have no IP, you cannot recieve any information, ie no internet. You should be able to communicate between the two machines on the hub using "hostnames" or the name of the computer, if you care, probably not, but you will only be able to go on the internet with the one computer that was given the IP first, meaning the Mac.

If you have a Router, the router uses the one connection to the internet and assigns its own IP's to all the computers on the network, effectively sharing the IP you are given and dividing it between all the machines on the network. Looking kinda like this crappy ASCII diagram:

{internet} <---> DSL IP - [router] <-->IP#1, IP#2, IP#3, etc., etc.

Hope that helps, you need to drop some cash, or your parents do, to get two computers on the internet using a router. Or routo-rooter as Enron would say. Get something like this, its what I have and its great. Don't bother with a Linksys, they blow Lich's.