I installed the XP and the Dell drivers on the laptop and installed a free bit of software called Roborealm which is a great visual processing program intended for robotic applications which just so happens to have an SCC-32 and a Sabertooth module in-built. Joy !!
(Update: Roborealm was free, but they have started charging for its use, luckily not too much)
There is an example green ball follower script that you can download from the Roborealm website that I modified slightly to work with my hardware and I spent a few hours tinkering with the settings in the filters until I had it as good as i could get it.
I also downloaded the free software, UltraVNC, on the two laptops which allows me to remote into the robot and make adjustments or just watch what is going on on the screen and webcam.