I was using a powered USB hub to power a USB external hard drive because the Pi cannot output enough power to power the HD itself.
I plugged the HD into the Pi and it looked like it was working, but I also plugged in the micro USB port too because the hubs power was being distributed to the HD and the pi. But by plugging in both I think I short circuited the Pi. And now it just shows the red light no matter how many times I reinstall the OS onto the SD card. My conclusion? I short circuited it.
What would be the correct configuration to using an external HD the Pi itself cannot power? (Without creating a short circuit.) I used a power usb hub that was recommended for the Pi.