Ever since the PS2, consoles have been designed to work either horizontally or vertically. However, the Xbox One is going to break that mold. Regardless of its plain, rectangular shape, the Xbox One is not work in a vertical orientation. Of course, nothing is stopping you from turning your console upright, but Xbox Senior Director of Product Management and Planning Alber Panello says this could negatively affect your console and games.
“We don’t support vertical orientation; do it at your own risk.” He clarified, “It wouldn’t be a cooling problem, we just didn’t design the drive for vertical. Because it’s a slot loading drive, we just didn’t design it for both.”
So why is Microsoft choosing to go down this design route? Well, according to Panello, eighty percent of Xbox 360 users keep their console horizontal. That’s an overwhelming majority. So, likely, it was only natural to save time, money, and effort by making it a horizontal loader only.
Note that while Panello says that the Xbox One is a slot-loading disc drive, there are slot loaders that work just fine vertically. The PS3, for example, slot-loads just fine from a vertical position. In addition, console orientation should not cause any issues when playing games off your hard drive, such as digitally distributed titles and indie games.
Source: Gamespot