What Windows 10 means for Microsoft investors

Microsoft rolls out Windows 10
Microsoft rolls out Windows 10
MSFT hopes for fresh air with new Windows
MSFT hopes for fresh air with new Windows
Windows: The timeline
Windows: The timeline

It's the Windows you know, only better.

That is how Microsoft describes its new operating system, which officially launched Wednesday.

For Microsoft investors, Windows 10 needs to be a hit. The franchise still accounts for some 25 percent of the company's revenue. And it impacts a lot of people: More than 1 billion users rely on Windows.

But expectations are muted. A financial bump from Windows 10 would show up in the company's Devices & Licensing group. Right now, Wall Street thinks sales in that division will fall 6 percent in 2016. Analysts have been disappointed with the most recent upgrades.

"The expectations are so low based on what we saw with Windows 8," said Patrick Moorhead, president and principal analyst of Moor Insights & Strategy. "I think investors will probably be surprised at how well they do. And also, it's the way Microsoft is accounting for Windows. They are being very conservative. They are saying it won't have an impact until next year. They are playing it very safe."

But Moorhead thinks Windows 10 will prove popular, pointing to all its new bells and whistles. There's an all-new browser called Microsoft Edge, allowing users to write or type notes directly on webpages and share them with others. Cortana, Microsoft's digital assistant, which responds to voice commands, also comes to the desktop. The operating system starts up and resumes fast; boasts more built-in security features; and it's designed to run across a wide range of devices including smartphones, tablets and PCs.

Read More

Microsoft bulls say the new operating system should excite developers, who can now write one software application for many platforms; allow Microsoft to cross-sell users on different services, from Office 365 to OneDrive; and spur PC sales in the back half of the year.

"I believe Windows 10 will spark a PC hardware increase in the fourth quarter," said Moorhead. "I don't think we will see that lift in the third quarter because that quarter will mostly be about the promotion of the upgrade."

Moorhead added, "I think people have to first realize the benefits of Windows 10 before they are inspired to buy a new system."

On the other hand, FBR's Christopher Rolland is skeptical Windows 10 will give a real boost to weak PC sales. That's because consumers using Windows 7 and Windows 8 can upgrade to Windows 10 for free.

Will Windows 10 help Microsoft get its mojo back?
Will Windows 10 help Microsoft get its mojo back?

"Consumers won't need to upgrade their hardware," Rolland said. "So, for the first time, hardware and software are truly disconnected in terms of purchase cycles."

Research firm IDC expects PC shipments to drop 6.2 percent this year, which would be the fourth consecutive year of declining volume as the PC market competes with mobile devices such as smartphones and tablets.

Beyond financial metrics and business strategy, analysts say the launch of Windows 10 is a critical moment for the reputation of CEO Satya Nadella, who took the helm of Microsoft in February 2014. He's earned praise for his decisions to focus on mobile technology, cloud services and .

But analysts say the launch of Windows 10 is a different kind of test for the CEO.

"Nadella will be tied to Windows 10," said Daniel Ives, an analyst at FBR. "If it's not successful then the optimism around the Nadella era takes a huge hit. They are betting a lot on this. So much of the growth, so much of the cloud-centric vision is tied to Windows 10. All eyes will be on the success of this platform in the next three to six months."

Microsoft has set ambitious goals. The software giant wants 1 billion Windows 10 devices in the market within three years. Wednesday is the start of that campaign.

Read MoreWindows 10 review: Microsoft steps back to move forward