Which Microsoft software would you like to see open sourced?

> Windows
> Office
> .Net

And if Microsoft were to open source any of these items would you dump your current open source offerings?

> tfw I know Microsoft could open source office and finally help kill the garbage that is Libreoffice.

I personally think Microsoft is being dumb. I mean open sourcing there software stack, especially with their hold on the PC market would be extremely beneficial.