Looks like you are connecting to the Arduino on Com3 and Pronterface is trying Com2. Pronterface should also look for the RAMPS on Com3
If the Arduino IDE is connected to the Arduino then Pronterface won't be able to, i.e. if you have the Arduino serial IDE open as per the first picture then Pronterface won't be able to access the port. Likewise if you have Pronterface connected to the printer the Arduino IDE won't be able to flash new firmware.
Steve