Internet sharing using a switch

I have an internet connection which I want to share between 2 computers. I bought a Netgear switch (8 port) thinking it will solve the purpose but it didn’t. Connecting the LAN cable from my modem to one of the switch’s port and connecting my computers to the two other ports, makes the internet connection work for only one of the computers at a time (which I think is the nature of the switch). Is it possible to still split the internet connection between the two PCs using some software based routing ? One PC runs WinXP and the other Linux (Ubuntu).