I mean... there's already ads in explorer

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F...

and:

  - ads on the lockscreen
  - ads as notifications
  - ads in the start menu
  - ads in the "change file association" dialog
  - ads in the apps (e.g. solitaire)

heaven forbid we critisise Microsoft for these things