turn off computer

Hey guys, I just built my first ever computer and got everything to work including installing High Sierra, except for my computer to stay fully shut down. I can turn the Computer on and off, but when I turn the computer off, I can click the mouse or a key on the keyboard and the computer turns...

I made a flawless install of ML no big deal, but when i finish install and boot, only boots with -v option and after install multi beast its freeze at apple logo. On lion everything install and work 101% I7 DH55tc Nvidia GT 520 16gb memory Greetings from Brazil