Whenever we’ve seen the Xbox One on display, either in promotional shots or during major events, the console has always been positioned flat. So if you’re looking to save some space in your entertainment center by standing your brand new Xbox upright you may be doing so at your own risk.
In a brief quote Senior Microsoft VP Albert Panello explained that the console’s disc drive was designed to be used vertically. Its slot based design is very similar to the self-loading trays found in the PlayStation 3, Wii-U and original Wii, and those consoles offer optional vertical stands. But, then again those consoles also probably don’t weigh as much as the upcoming Xbox One.
To GameSpot Panello Said:
“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.”
Source: Joystiq