Help! My arduino doesn't recognize on any of my port..

my computer doesn't recognize my arduino UNO board on any port. I tried to
change the serial port on the Tools menu but it didn't work.

here's the error..
avrdude: stk500_recv(): programmer is not responding

furthermore, whenever I connect it on my computer,
the LED near PIN 13 and GND doesn't blink anymore..

is there any other way to fix this or should I replace the my arduino board?
tnx. in advance..