Did Windows Just Collapse?
If your smartphone or tablet is a real computer, then Microsoft's share of computer sales has plummeted from 96% to just 35%. Here's the chart from Cult of Android.
The problem is with how you define a computer -- and I think that comes down to usage.
A ten-inch tablet is probably a perfectly good laptop (or even desktop) replacement for most people. The only things it doesn't do well is store a metric crapload of files, or rip video. I also find that if I'm writing something longer than 300 words or so, I prefer to use a bluetooth keyboard instead of the screen. But essays, DVD rips, and terabytes of home-ripped DVD aren't something a whole lot of people do.
A seven-inch tablet is mostly a "media consumption device," as critics labeled the original 10-inch iPad. Held in portrait, the keys are too close together for touch typing. Held in landscape, and you can't see enough of the screen. For reading, watching TV, or playing Angry Birds, a Nexus 7 or iPad mini is all you need. It's still a laptop replacement for a certain market sector, but a smaller one.
And your smartphone? Fuggidaboudit. It's a phone. It also does some great things (Star Wars Angry Birds comes to mind), but it's just too small to replace anything. What it does is take a formerly single-purpose device (your phone) and turn it into an electronic Swiss Army knife of fun. I wouldn't part with iPhone, but it can't make me part with any other device, either.
That's where the comparison falls apart. People don't buy phones to replace their computers, so it's silly to include them in a chart of computer marketshare. Tablets are a threat, but only a limited one -- for the time being, that is.
So, no, Microsoft Windows hasn't dropped to 35% of computer sales. It is still the king of desktop and laptop computing. But that doesn't mean MS has nothing to worry about. They've failed to gain any penetration into mobile computing. Windows Phone 8 is a solid performer, but Android and iOS have already carved out the top and bottom of the cellular marketplace, leaving Microsoft's late bloomer nowhere to squeeze in. And Surface... well, it's headed towards a bargain bin near you.
Assuming there's a Best Buy near you, which is becoming increasingly less likely.
Microsoft has missed out on the only growth market in computing today. It's doubtful anything can knock Windows of its desktop/laptop roost in the medium term, but that's no longer where the big money is.