Why Arduino Mega 2560 throw error when i try to upload example
I install driver for this site and everything is working well.
driver download:  wch.cn/download/CH341SER_EXE.html 

I'm recommend to unplug arduino first and install driver, after that plug and enjoy.

Here is a video:
https://www.youtube.com/watch?v=FhmG5J-AHrg