Translation:Whose computer is this?
Who's computer is this is perfectly acceptable and is more natural than whose.
'There is cars.' vs 'There are cars.' People tend to make the mistake of using the first sentence, but that does not make the first sentence correct. Similarly, 'whose' shows a possesive and 'who's' is a shortening of 'who is'. Just because people regularly make that mistake does not make it correct.