In aviation, life critical systems (such as auto-pilots) never use Microsoft/consumer grade O.S.'s. PC style hardware architecture is not inherently life safe so the computers tend to be custom/bespoke designs and they almost never get caught up in fiasco's such as the present one.

This is why Stuxnet was such a significant piece of malware - it was one of the first known instances of industrial computers being targeted by malware - again, another lovely piece of code written by the US Govt.

Even in non-critical area's such as In Flight Entertainment, aircraft avionics designers are loath to use MS operating systems - the only brand that I can recall that did, used Windows CE and then it wasn't overly successful & eventually was bought out, shot & buried by Panasonic. Non critical avionics systems have mostly been Linux based (I can not speak for the latest line of Boeings). I've even seen avionics PC's running a single application written for windows but running on Linux via WINE - and that's the way it came out of the factory. 

I can not speak for the design of "Smart Car" computers, however I imagine they face similar certification criteria and I expect that rather than reinvent the wheel, they will look for inspiration to aviation where it has been done for years. There is no reason to assume cars are or will be using PC operation systems, as computers have been in cars for years, and never done so to date.