Microsoft has just announced it reimagining of its operating system, and an early preview version of Windows 10 will be available to download as soon as this week.

Announced by Windows chief Terry Myserson on Tuesday in San Francisco, Windows 10 is the company's broad play for mobile and desktop for the next couple of years. Windows 10 will run across devices with screens from 4in to 85in and even some devices with no screens at all, such as servers and Internet of Things products.

However the final release of Windows 10 to the public won't happen until the middle of 2015 at the earliest, with Microsoft's only guidance being that it will happen after the company's Build 2015 conference for developers, which takes place in April.

Ahead of that however, Microsoft is going to open up a preview of the software to anyone who wants to try it out, with the Windows 10 Technical Preview.

How to get Windows 10 Technical Preview

The Technical Preview is not going to be a polished, slick piece of software and Microsoft warns that only "PC experts comfortable downloading unfinished software" should consider using it, and should only install it on a secondary device.

Microsoft is hoping to use the feedback from this Technical Preview to help evolve Windows 10 before it finally launches.

"We hope to involved tech enthusiasts in our software development process over the next several months so that your feedback becomes part of the next version of Windows," Joe Belfiore, who heads up Microsoft's operating system experience team, says in a video introducing the preview.

The Technical Preview will be available to download from the company's new Insiders Program website which goes live on Wednesday, 1 October. While Microsoft hasn't given any exact time yet, sources suggest the website will go live at 7pm UK time on Wednesday.

The Enterprise Technical Preview (Build 9841) will be available to download once you sign up to the Insiders Program, and Microsoft will push regular updates to those on the program in the coming months.

Microsoft will also want some feedback from users about what they like and don't like, in order to tweak the final version of Windows 10.

Consumer Preview

The Enterprise Technical Preview will only run on machines using an x86-based chip, which means that for now at least it won't run on the majority of tablets and smartphones, which use ARM-based chips.

Microsoft said that a consumer-focused preview would be arriving some time in early 2015.

The Enterprise Technical Preview will get a lot of the new features which were announced on Tuesday, including the returning (and redesigned) Start Menu, Snap Assist, virtual desktops and the ability to run Metro-style apps on the desktop.

What won't feature is the new Continuum mode, which allows for easy switching between touch and desktop modes on two-in-one devices.