The Xbox One is not a machine that should be stood vertically, according to Microsoft.
This, according to Microsoft’s senior director of product management and planning at Xbox Albert Panello, is due to its use of a slot-loading disc drive.
"We don't support vertical orientation; do it at your own risk," he told GameSpot. "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."
He added: "We found, interestingly enough, that 80 per cent of people, believe it or not, have their Xbox [360] horizontally."
The site notes that both the original ‘fat’ PS3 and its first ‘slim’ redesign used slot-loading trays and were able to be used while standing vertically.

http://www.mcvuk.com/news/read/micro...ically/0121405