Arduino not responding
I'm personally not really in to this RTFM kind of answer, but in this case it really do answer most of your questions about the bootloader part: http://arduino.cc/en/Hacking/Bootloader

About the error, a quick search on SO gives you this: https://stackoverflow.com/questions/24240285/arduino-nano-3-avrdude-stk500-getsync-not-in-sync-resp-0x00