what ftdi windows driver for arduino nano at http://www.ftdichip.com/FTDrivers.htm they seem to divide chips into two categories,  FT4222H vs. D2XX driver. 

What's the correct for a arduino nano?
The Official Arduino Nano has an FTDI FT232RL.

You want to use the Virtual Com Port(VCP) Driver so the FTDI device appears as a COM port under windows.

See the getting started guide for details.