Unresponsive Arduino Uno

I just received the starter kit a few days ago. Everything was working perfectly until about 15 minutes ago.

After building the DC motor circuit exactly how it is shown in the example, I hooked up a 9-volt battery to the board, and the motor didn't turn. So I plugged in a 12-volt DC adapter, and the motor worked a little too well. It frightened me a little; I unplugged the power source.

Now, no matter what I connect the board to, USB or otherwise, the TX and RX lights remain on constantly, and the reset button doesn't work at all. The board is unrecognized by Windows, and it won't allow me to re-install the driver.

The Arduino IDE only says that the board on COM4 is not available, and no further information could be gathered even with verbose output during both compilation and uploading.

Can you tell if it's still running the same sketch you last uploaded? Like, if you hook up the motor again, does it work? It's possible you got a new COM port when you plugged it back in.

After connecting it again, every on-board LED dims, no current seems to run through the motor.

Can you upload a sketch from the Arduino IDE?

If not so: while the IDE status says "Uploading...", double press the reset button on the board.

My Arduino Robot once went unresponsive too, and this solution brought it back.

The moment it starts uploading, it says the board is unavailable.
The menu item to change the port is grayed out.
Normally, upon booting, the TX and RX lights flash, then the LED connected to pin 13 will light up.
Now the TX and RX LEDs are just constantly on.
It will still light up an LED, but I am unable to upload a sketch.

Was it wired up exactly as shown in the picture here? http://learn.adafruit.com/adafruit-arduino-lesson-13-dc-motors

Yes, but I changed the code a bit, so it would send 100 to the motorPin, instead of reading from the serial monitor.

Gadict: Yes, but I changed the code a bit, so it would send 100 to the motorPin, instead of reading from the serial monitor.

That wouldn't cause any problems. The motor in the kit can pull more power than the Arduino can supply directly, which is the need for the transistor and diode, as explained in the training material. So, as long as it's wired up exactly like in the picture, the Arduino should be 'protected' from excessive current draw from the motor. You're essentially building a simple electronic speed controller.

This setup should not be capable of burning out the Arduino, but it sure does sound as if yours might be bricked. IMO, that should not happen, so if you're sure you wired it up correctly, I would call the company you got the kit from, and see if they might replace it for you. They may also know of a trick to revive it. Check your wiring real carefully before doing that though.

Aw, man. I was hoping I wouldn't have to order a new chip. Oh well. Thank you for you help. :)

I was hoping I wouldn't have to suggest that it might be dead, but it might. Not certain, but it's a possibility.

I ordered a new, pre-programmed chip from Adafruit. After installing it, it has the same problem. The TX and RX lights stay on, unless powered by a new 9-volt battery, and even then the board does nothing, not even running the blink program that should be installed. The reset button still does absolutely nothing, and it will not allow me to install a driver to the board.

Also, the Device Manager says that "Windows has stopped the device because it has reported problems. (Code 43)"

Wow, I really don't know. What did customer service say about it?