how can i compile microsofts code? and there are easily systems which are so complex if you compile them the wrong way, you get other behaviour or more bugs.

and it may be also human error, not a conspiracy theory. if you do not have the source code and the recipe to build it yourself than you can not guarantuee that the inspected sourcecode (which was given to you either by disk or by a datablob over the internet) is the binary which you are currently running on your windows.

hell, perhaps they shipped an update which broke an security measure, and the update was shipped after you inspected the source.