How does the reset button work on the Arduino?
The reset button does pretty much the same as unplugging the board and plugging it back in.  It restarts your program from the beginning.  

The same thing happens when you program the board - the USB interface presses the reset button for you.  That then enters the bootloader for a second or two so it can try and program it.

When you reset the board the LED on pin 13 should flash a couple of times while it's in the bootloader before it runs whatever program you have programmed in.  If that LED doesn't flash when you press the reset button then there is a serious fault with your board which will take further diagnostic.


If you have anything else plugged into the Arduino then unplug it.
Try powering the Arduino from different power supplies.
If you have another Arduino or an AVR programmer try re-flashing the bootloader.