When having troubles to program your Arduino, please make sure:
(1) It is properly powered (via the USB cable for instance)
(2) No components or accessories are interfering with the serial line (pins 0 and 1)
(3) The Arduino drivers are properly installed in Windows ( [arduino.cc/en/Guide/windows](http://arduino.cc/en/Guide/windows) )
(4) There are no short circuits.
(5) It is not running code that might interfere with the programming (e.g. using the serial line at all times). If this is the case, pres and hold the reset button, click the Code upload button, and release the reset button once the program is about to go out (once it finished compiling)
(6) You are using a simple program such as Blink to test the programming functionality.
If the problem persists, please let us know as this means that your Arduino is probably defective (if you were never able to program anything) or damaged (the microcontroller stopped working after some specific action).