Hello guys. I am new to the forum although i have been a lurker for quite sometime. Last month, i got a Retina Macbook for my wife as a Xmas present. I remember clicking on the "about this mac" and it shows the macbook comes installed with MacOS Sierra. Today, i checked again and miraculously, it is now MacOS El Capitan. I clicked on software update and it is allowing me update to Sierra. What gives? Did the OS downgrade itself? Should i update to Sierra now? What if if happens again? Anyone encountered such problems? Thanks in advance. This is my 1st foray into Mac computers having been a lifelong windows user. So amy help is greatly appreciated.