The global launch of Windows 10 is a pivotal moment for Microsoft as a consumer business, because in recent years Windows has started to matter a lot less.
The rise of mobile devices has hit the PC market hard – and no more so than Microsoft, which has around 1.5 billion Windows customers, making it the market leader in that arena.
This, combined with Apple’s OS X and Mac computer line-up regularly bucking the trend and actually increasing sales, has left Microsoft and Windows adrift in the technology world, with Google’s Chrome and Android dominating.
But a hint of change appeared at the beginning of the year when Windows 10 was first previewed, and it has hinted at a potential change in fortunes for the firm.
The core features of the update – Microsoft Edge, Cortana on desktop, Continuum and the idea of the software working across all Windows devices – sparked interest arguably not seen in Windows since the pioneering days of Windows 95.
But it’s only the beginning, and Microsoft must get several things right to start it on the road to success again.
These features now have to live up to their impressive stage demonstrations in the real world – Edge must be fast and easy to annotate as suggested, while Cortana must continue to be a seamless and intelligent assistant across a new range of devices.
The gaming streams from Xbox One to PC are also going to have to hold up well if Microsoft wants to entice developers on to Windows 10.
If Microsoft can get the core of Windows 10 right, it could begin to excite and encourage developers back to the platform.
The promise of one version of an app that works across phone, tablet and computer with minimal work is an enticing one for coders, but developers are still curious about how much effort this will actually take.
Make it easy, and the Windows platform could begin to flourish the way Apple’s has in recent years as developers fight to get involved.
There are more than a million apps on the Apple App Store, in comparison the Windows Store which around 500,000.
The health of the Surface brand – Microsoft’s tablet-laptop hybrid – could also have a say in the success of Windows 10.
Having steadily gained on the iPad in the last year, the growth of the Surface business to almost a billion US dollars (£640 million) was one of the bright spots of the firm’s most recent financial results.
If the hardware running Windows 10 is performing well, the developer community is far more likely to want to build on it.
Not an area the tech giant is currently focussing on too heavily, but as high-end flagship smartphones continue to sell in their millions, Microsoft will have to return to them in earnest soon.
The Lumia is performing OK in the lower and mid-range arenas, but a company the size of Microsoft really should be looking to take on Apple, Samsung and co in the premium market.
The Windows Phone has been something of a five-year struggle, with sales never taking off – squeezed out by the aforementioned rivals. But a solid base provided by Windows 10 could be a springboard for new and better hardware.
The public reaction, therefore, as Windows 10 rolls out from Wednesday has never been more important to Microsoft.