I cannot quit the game in normal conditions. I get a black screen and then the computer doesn't answer at all. Using Ctrl+Alt+Del doesn't work; Alt+Tab doesn't work either. The only way is to shut down the computer the brutal way, by pressing the on/off button until it shuts off...
My computer is this one:
http://www.msi.com/product/nb/GX60-Hitman-Edition.html#hero-specification with Windows 7 as the main OS (bual boot with W10). The game normally runs on ultra high settings but I lowered down the shadows quality; the rest staying on high.