[hjkl0]

You give Apple too much credit, and Microsoft too little.

The common conception is that Microsoft created the “flat UI” thing wholly from scratch, it was seen as totally original and unique at the time, it took no obvious immediate influences from contemporary software design trends.

[jamincan]

I think the Windows Phone was the first from Microsoft with the flat UI. While it didn't take off, I remember a friend who had a Windows phone and thinking how radical and different its UI was.

[fifticon]

Though not contemporary, Windows 3.1 and Windows 2.0 beg to differ, as do Motif and Athena Widgets.