On January 21, Microsoft officials said to expect the latest Windows 10 Technical Preview test build for desktops to be available within a week.

On January 23, the Operating System Group made good on that delivery promise, making the January Technical Preview build of Windows 10 for desktops available to its Windows Insider testers.

To be clear, this is not the first Windows 10 test build designed to run on Windows Phones and small (under eight-inch) Windows tablets. That Windows 10 mobile SKU won't be available to testers until some time in February, Microsoft officials confirmed this week.

The January preview is build 9926. In order to install it, testers first need to apply this update to the November tech preview, which Microsoft initially made available in December 2014. Registered Insiders can get the latest test build from the Preview Download site starting at 1 pm ET/10 am PT today. The new January build also is available in ISO form.

The January Windows 10 Technical preview includes a number of new fixes and features that Microsoft introduced since its last publicly available Windows 10 technical preview (Build 9879), which the company launched in November 2014.

The January preview includes Cortana integration, allowing users to use Microsoft's Cortana personal digital assistant technology to use voice or keyboard input to set reminders, find information stored on their PCs and tablets or search for information on the Web.

It also includes support for Continuum, the technology that allows users to switch more seamlessly between tablet mode and PC/laptop mode. When using in tablet mode without an attached keyboard, the Start menu becomes a Start screen and windows apps go full screen.

The new Start menu that Microsoft officials showed off on January 21 is part of the latest tech preview build, as is the much better organized Settings menu. The new Xbox, Photos and Maps app previews, the Windows Store beta, improvements to wireless audio and video connectivity are all part of this January Windows 10 preview build, too. And the Charms bar from Windows 8 is gone (huzzah!) and is replaced by the new Action Center in this build.

The January preview doesn't yet include Spartan, Microsoft's new "modern" browser. It also doesn't yet include support for the OneDrive-based Music Locker, which Microsoft officials mentioned earlier this week would be coming to Windows 10.

Currently, the Windows Insider program is geared toward testers who want to try out the latest Windows 10 bits. But Microsoft officials hinted that Windows 10 software development kits and related development tools may soon be available via the Windows Insider program, as well.