Remove all the stepper drivers and power up. If it doesn't power up, you know you damaged the RAMPs itself. If it comes up successfully, power down and add one stepper driver and power up again Add one at a time until you see the failure.
Do NOT connect or disconnect either a driver or a motor while power is on as this will most likely kill the driver.
Have you tried the ardiuno itself with the PC? Since it's hte USB connection that's bringing your PC down, and since the RAMPS has no USB circuitry on it, I'm skeptical of the arduino itself.