Are you trying to capture from a console plugged in to the PC?
or from a game running on the PC itself?
From your post I think your capturing from an external console, if so I think the issue is that VirtualDub is expecting to capture from a digital source through the firewire port on your computer, but you are connecting an analogue source through a composite video input.
To capture from this analogue source you'll need another program, iuvcr (trial version from here: http://www.iulabs.com/iuvcr/download.shtml) is a good option for doing this, it has a lot of options but there's probably a pre-set which will be ideal for you.
You could also use the TV capture software on your Vaio if it has something like that.
Panasonic SD9, Panasonic NVGS-75, Canon MV600i