what does this error mean (avrdude: stk500_getsync(): not in sync: resp=0x00)

Thanks Arrch
I unplugged and a new port COM3 pulled up but when I plugged back up it still creates the same message.
I guess I have to figure out which of my USB ports is the actual COM3 (I have 5 USP ports) how do I find out which one is COM3 pointed at?