Arduino doesn't turn on please help

Hey guys, I'm 15 and I'm quite new to arduino. The Board I have is the Arduino Mega 2560 R3. it has been working fine for years now. I recently embarked on a new project, a robot RC car inspire by this project : http://www.instructables.com/id/James-Your-first-Arduino-Robot/ . I plugged a prototyping shield on my arduino and started wiring, while the board was plugged into the computer. Then I sensed it stopped working. the green light turned off. I touched the board and the 501v chip near the usb input was really hot. I think that the smd component is a fuse (the 501v chip). then I plugged the board into my moms computer and it worked for a moment and stopped again, and once more the 501v chip was extremely hot. I then plugged in a 9 volt batter to the dc power input, it still didn't work. I'm helpless friends. please help me if possible.

We need circuit diagram How you connected. Please disconnect all connection ; upload simple blink example check it working. Make ensure nothing being connected.

Now check Whether IC gets heats up or not. If not getting heats up means board under working condition ; if heating that means you destroyed USB to TTl converter IC .Need to time replace

I did connect it to the computer with nothing connected. Only the fuse gets hot. the arduino doesn't turn on at all.

CHeck voltage @ 5v pin & 3.3v pin whether you getting voltage odr not. If not The 5V regulator ;OPAMP ; USB to TTL IC got burn out