Windows are a popular operating system

The other day Emily was playing Webkinz on our laptop. When she shut down the computer, she was reading the screen and said "Dad, I think I found a mistake. It says 'Windows is shutting down'. Shouldn't it be 'Windows are shutting down?'" This observation from a 7-yr-old amazed me but what amazed me even more is that she totally understood when I explained to her that normally she would be absolutely right, but in this case, Windows is singular because it's the name of one software product.