Hi just signed up here, I do have a laptop in my TJ just for offroad use.
I have used Garmin08 but now running Microsoft Streets and Trips 2007 soon 2009. I found that Microsoft had better info but no topo for running trails.
I found MS had state land and marked trails in the map! Not with Garmin just paved roads in Northern MI.
I ran a simple setup to mount the laptop and video camera.
look here for info. I'll refine the mount later.
clicky link