I am a total newbie with Arduino Board,recently I bought an Uno and it was working perfectly along with uploading codes and everything worked fine.
I was working with an external 12v power source accidentally the Vin pin was shorted with the +5V pin on the Uno as i was doing all the connection through a breadboard.
As of now the code is burned the device can be connected with a PC and it shows up on IDE with correct COM ports even I can Access the board info from IDE the serial monitor works fine only thing I'm not able to do is upload any sketches even the basic examples whatsoever is it something to do with the boot loader?
While i Upload any sketch I'm getting this error " avrdude: stk500_recv(): programmer is not responding"
It's not clear to me from what you wrote, is the last sketch you uploaded to the Uno still working as expected?