Easy GPS, GeoBuddy, and GSAK will talk to the 12 (as will most others). I suspect your laptop has no serial port? Just get a USB-Serial cable and your good to go.
As for older gear, I have a III+ but it just hangs out in the computer room keeping our network time synced up.
Thanks for that, I am using a GPS12 and was looking for some way of managing the waypoints better. I had a a dabble a few years back but couldn't find anything which worked properly on the 12...