Not able to communicate with Arduino Mega 2560.

Hi, I am having trouble getting the Arduino Mega 2560 recognized by the usb ports of my windows 8 computer. It was working fine before. I was using it along with the Adafruit motor shield to drive a couple stepper motors and a servo motor. Now, windows is not even recognizing the plugged in usb. I have followed the troubleshooting guide but still can't get to work.I have disconnected the motor shield. When I plug in the usb, the led near pin 13 is on and so is the "on" led. When I press the reset button, the led near pin 13 blinks once and then stays on. I have even tried another usb cable. Anyone have any ideas?

Try this instructions:

http://forum.arduino.cc/index.php?topic=178994.0