Microsoft (NASDAQ:MSFT) will unveil Windows 10 on Wednesday. At a special press event, the Redmond-based tech giant is likely to reveal several key details of its next operating system, including the release date and pricing policy.

But much is already known about Microsoft's next operating system: the Windows 10 technical preview has been available since October. At the same time, several reports and comments from Microsoft executives have shed light on the direction the company wishes to take its operating system in.

Below are four of the most important details investors should know about Windows 10 heading into Wednesday's event.

The start menu is back
Since 1995, every version of Microsoft's operating system had centered around the start menu, creating a familiar interface for hundreds of millions of loyal PC users. But that changed with the release of Windows 8, which ditched the start menu in favor of a new, "modern" interface and charm bar.

Fans of the start menu will be happy to know that Microsoft has brought it back for Windows 10. To be clear, it isn't exactly the same start menu found in Windows 7 -- it's enhanced with live tiles -- but it offers almost identical functionality.

The absence of a start menu in Windows 8 generated a fair degree of backlash, and may have prompted millions of users to stick with Windows 7. Its return could reinvigorate the PC platform, and entice millions to upgrade.

It won't be as fragmented as Windows 8
In addition to its non-existent start menu, Windows 8 has often been criticized for its dual interfaces (tech reviewer David Pogue argued that Windows 8, was in fact, two distinct operating systems combined into one confusing mess) which often don't play well together. Some of Microsoft's apps, for example, work only in tile mode -- filling up the screen and offering an interface that's clearly designed for touch input. Others work as they always have, still optimized for a desktop, mouse, and keyboard. Jumping back and forth between the two can be a confusing, and at times frustrating, experience.

Windows 10 corrects that problem -- now, modern apps open in a familiar, windowed-fashion, allowing desktop users to easily drag and resize them, as they would with any traditional Windows app.

Windows 10 offers a feature -- continuum -- that intelligently switches back and forth between the two interfaces depending on the input methods detected. Plug a mouse and keyboard into a Windows tablet, and Windows 10 will automatically shift to a traditional desktop interface.

It could include a new browser
Although it hasn't been officially unveiled, Windows 10 is widely expected to ship with two browsers. The first -- Internet Explorer -- will offer a familiar experience to longtime Windows users. The second, codenamed Spartan, is a light-weight web browser that will offer an experience on par with Chrome and Firefox, according to ZDNet's Mary Jo Foley.

That could mean support for extensions, such as AdBlock Plus. Chrome's robust ecosystem of extensions allows users to customize it with additional functionality, and gives it a key advantage over Microsoft's Internet Explorer. Spartan might also offer several new features, such as support for Microsoft's digital personal assistant, Cortana, as well as pen input.

Despite making a number of improvements over the years, Microsoft's Internet Explorer has seen its popularity wane. Last year, it was overtaken by Chrome in the U.S., and it's been increasingly challenged by Safari in the mobile space. A new browser could help Microsoft recapture some of its lost users.

It will have a strong focus on gaming
Windows 10 will run across all of Microsoft's devices, including its game console, the Xbox One. Phil Spencer, the head of Microsoft's Xbox division, is scheduled to present at the event, and has already declared that Windows 10 will be the best operating system Microsoft has ever created for gamers.

What that means is open to interpretation, but it could imply that exclusive Xbox One games -- such as Halo: The Master Chief Collection -- will come to Windows PCs. The Xbox One itself is built with only semi-customized PC chips, and with Windows 10, could be transformed into just another PC -- albeit, one with an interface designed to work with a controller.

For Microsoft, turning the Xbox One into a PC could be the culmination of its Xbox project, which at times has been criticized by investors as a wasteful side show. Getting a Windows PC attached to millions of televisions could allow Microsoft to head off any rivals' -- Apple, Google -- attempts at taking control of the living room.

Can Microsoft save the Windows platform?
Although Windows remains the preferred operating system for hundreds of millions of PC users the world over, Microsoft's long-standing dominance is challenged. Its attempts at breaking into mobile have largely been a failure, and as rival platforms -- iOS and Android -- continue to evolve, Windows could struggle in the years ahead.

Windows 10, however, could reestablish Microsoft's dominance. Investors in the space should keep a close eye on Wednesday's event.