Not possisble. Capture only works over a firewire cable from a camera with firewire out.
I would guess that Dell preloaded a Webcam capture utility onto your computer. You should be able to use that, then Save the resulting file in a format, that PrPro can edit. Look into a Webcam utility on the computer, and then tell us what options it has for the video capture, and someone can help you pick the best format/CODEC.
You're better off using a normal camera for this. Most web cams take crap video (by comparison) and offer little to no control of anything other than start and stop.