My boss just gave me his old compaq folding keyboard p/n 249711-001
The plug is the same as it is on my XV6600, but I plugged it in and just didn't seem to do anything. Do I need a driver as well (and where could I get it?), and are these devices even compatible?

yes you most likely need a driver.

google the keyboards model number and "driver" to see the results. may even want to use "PPC" or "smartphone" in the search $tring...