My Arduino Shorted

I Powerd my Arduino Using 12V From The power jack and i conected 5v to ground the leds are working but i cant proggram it
And the proggram is not running
Can Someone Help?

I had a similar issue that seriously crippled my mega (clone), but surprisingly didnt completely kill it.
When I plug mine into the computer, it would no longer recognize the device.

It destroyed the voltage regulator, which I removed (so I can only use 5v as the input).

I thought it was completely dead, even though the on light and led 13 light came on, and it would flash if I pressed the reset button. I couldnt tell if my program was running or not, still had a bunch of debugging to do

I have a rs232 to usb adapter to program a pro mini so I connected that up to the mega and was able to reprogram it with the blink example. It seems my issue lies somewhere between the usb plug and/or the onboard ftdi chip (or whatever its called)

If you have the usb to serial adapter, youd connect
(Ftdi - arduino)
5v -5v
Dtr-reset ( use a 0.1uf capacitor instead of a wire)
Tx- rx

The other pin on the ftdi isnt used