The computer giant has surprised many people by naming its newest operating system Windows 10.
Have the clever people building Windows forgotten how to count? Unlikely.
After criticism of Windows 8, it seems the company is trying to make a point that the new release is a big one.
"Windows 10 will be our most comprehensive platform ever," Terry Myerson, head of the operating systems group, explained.
"It wouldn't be right to call it Windows 9."
While the multi-tile based interface of Windows 8 worked well enough on phones and tablets, desktop users found it a struggle.
With Windows 10 Microsoft is trying to make a truly tablet, mobile and desktop friendly operating system. So what's new?
The main selling point for Windows 10 seems to be that it will work "seamlessly" across all devices.
New Universal Windows apps will offer "the same experience" on PCs, tablets, phones, and Xbox One. Developers can use the same coding language to create each version.
Microsoft says it wants to be "the first in the industry" to make it easy to build apps across different devices.
The start button is back. And this time, it's personal. The bottom-left icon has been around since Windows 95 but was ditched in Windows 8, only to be replaced in Windows 8.1 after an outcry.
Users will be able to customise the start menu and add live tiles detailing how many emails you have, how warm it is outside or when your next appointment is.
Is it a laptop? Is it a tablet? With so many 2-in-1 devices now promising to provide touch screen fun with a keyboard for typing boring work stuff, Microsoft reckons it's come up with a nifty way of switching between the two. Unplug a mouse or keyboard and Windows will ask if you want to enter tablet mode, resizing apps and stripping back the display accordingly.
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It's almost like Microsoft wants to forget Windows 8 ever happened.