VinRouge:
Microsoft? I take it you dont work with Aircraft. The 'operating systems' consist of multiple redundancy lines of code that are optimised for reliability and we dont use any recognisable operating system on modern aircraft. For example, all a FADEC does is map parameters to a fuel flow and inlet guide vanes; it is not required to send email!
As far as there anything like an OS, I would put my money on VxWorks. NASA used (are using it now?) it on Mars. Very reliable. I think both Boeing and Airbus have VxWorks running in some of the computers in their aircraft fleet.
Bob.