Customers running Windows 7 and Windows 8.1 will be able to download the software.
From July 29, customers running Windows 7 and Windows 8.1 will be able to download the Windows 10 software for free for a one-year period.
Microsoft will keep the operating platform current for the supported lifetime of the device. Customers can now reserve a free copy to upgrade.
Windows 10 includes a combination of old and new features. Most notably, the platform will see the return of the Start menu. It will also bring a new browser, Microsoft Edge, to replace Internet Explorer, as well as integration with Cortana.
In addition, Microsoft claims that Windows 10 is the most secure platform ever due to integration with Windows Defender and a lifetime security update commitment.
"We designed Windows 10 to create a new generation of Windows for the 1.5 billion people using Windows today in 190 countries around the world," wrote Terry Myerson, Microsoft’s Executive Vice President of Operating Systems, in a blog.
He continued: "With Windows 10, we start delivering on our vision of more personal computing, defined by trust in how we protect and respect your personal information, mobility of the experience across your devices, and natural interactions with your Windows devices, including speech, touch, ink, and holograms.