Can a PC connect to an Arduino for serial communication without installing the entire dev kit? I'd like to send a prototype board to a friend pre-programmed and wired. Ideally they should just need to plug in the USB and connect to it over a serial COM port. 

With another laptop I used for testing I had to install the full dev kit, sketch editor and all to get it working.

Can I somehow send just the portion of the kit that provides the COM drivers and not the rest? Is there a prebuilt install for just that portion?
On Windows in C:\Program Files\Arduino there is a folder called drivers, which contains all the drivers for the Arduino boards. I think that's what you are looking for.