The next version of Windows, codenamed "Threshold," is going to include some fairly major user interface changes beyond the inclusion of the new Start menu and "Modern" app windowing.

A couple of reports from earlier this week cited some other interface changes coming to Threshold. My sources are corroborating those reports.

First up, as reported by Brad Sams at Neowin.net, Microsoft is moving toward adding virtual desktops to Threshold, the Windows release expected in the spring of 2015. As Sams noted, other operating systems, including Apple's OS X and Ubuntu, already support virtual desktops, which allow users to run and switch more easily between apps and groups of apps.

Virtual desktops will allow users to run their apps in different spaces which they will be able to view one at a time. I'm not clear whether the virtual desktops functionality will be clearly and readily available to all Threshold users or if Microsoft will make it more of a hidden feature discoverable by power users.

The other UI change coming to Threshold is the elimination of the Charms Bar, as first reported by Winbeta.org.

The Charms Bar — an overlay that provided access to search, sharing, the Start screen, hardware devices and settings — has been a controversial feature since it debuted in Windows 8.

Winbeta suggested that Microsoft might eliminate the Charms Bar for desktop users, not tablet users. But my sources say the Charms Bar will be going away completely for all desktop, laptop and tablet users with Threshold.

Existing "modern" Windows 8 apps will get title bars that include menus that have the charms components listed. Settings already has its own tile (it's part of the default Start screen since Windows 8.1 Update). The concept of "contracts" — or agreements between apps — will continue to exist, even once Charms are gone, my sources say. But apps will need to include a share button to provide the same functionality as the share charm, if developers want to add that feature.

I've heard from my sources that Microsoft is hoping to deliver a public preview of Threshold some time in the fall of 2014. The goal with Threshold is to make Windows 9 more palatable for those still using Windows XP, Vista and Windows 7 , especially business users and those who aren't relying solely on touch for input.