Please resist to the urge to come up with anything that looks as though it could be MSFT branding.
Logo concept 1 would be an example of this, however I chose it because the coloring, simplicity and mood it evokes is very close to what I'm after.
Logo concept # 2 provides a decent example that I might like to see expanded upon. What I don't like about the logo is that it is too colorful and I don't like that the buildings seem to be trending downward - not something we want to evoke!
The third logo concept is really close to what we want to evoke however the bg color needs to be a lighter blue and the tree shouldn't look so distressed and appearing as though it's standing up to a cold winter.
Also, I am interested in seeing a concept that looks like an abstract stack of windows (no more than 3) where the front facing window provides the obvious window expression and the remaining two windows are simply offset in the background.
Finally, if you have what you believe to be a winning concept but it's not within the constraints I provided, let's have a look.