Interesting (to me) was that revenues for the same quarter in 2014 were $23.4 billion, or 5% higher. I don't follow MSFT that closely - read: almost not at all - but isn't it unusual for their revenues to fall?
At least to date, OS and Office revenue is somewhat dependent on those products' ship cycles. A recently released new version (or the end of support for an old version) generally drives upgrades which mean revenue fluctuates up and down not just on a seasonal basis but over a longer timeframe.