You can setup internet connection sharing to get them both online at the same time.
In order for it to work the Ethernet cable has to be a cross-over cable.
Connect the cross-over cable to the ethernet cards on the pc and laptop.
On the pc system go to Start > control panel > Network connections >
On the right side click on the "Setup a small work or home network"
That will bring up the network wizard follow the on screen instructions for internet connection sharing.


