To coincide with its Build developers' conference opening keynote, Microsoft has made available its Windows 8.1 Preview edition for download for free.

Aimed at experienced Windows user, says Microsoft, the preview build of the Windows 8 update is available from and can be installed whenever you like, although you should be warned that, because there might be bugs, you should create a recovery drive first, in case you need to restore back to the last version of Windows.

The software was demonstrated during the keynote, with a number of new features highlighted - including the return of the Start button. Cheers and applause even rang out during the event when that was announced.

Microsoft has now made it entirely possible to ditch the Modern UI altogether, or at least create a Windows experience which means you never have to use it if you don't want to. It's now possible to boot straight to desktop and use that brand new Start button, meaning you get a more traditional Windows experience. Alternatively, you can create a custom startup screen which shows all your apps, so you can open things straight away.

Live tiles have changed, showing more information and being more adjustable in size. Then there is the ability to set your own backgrounds to the Modern UI start screen, so you can have your holiday photos behind live tiles.

The camera is accessible from the lock screen now and Windows 8 has been given an improved camera app, making it better to use with tablets. The same applies to the PC settings menu, which can be accessed much quicker from the modern UI, not requiring you to navigate via your desktop.

Microsoft has lifted limits on Windows 8's displays, meaning we should start seeing Retina display resolution screens on laptops. Those displays can also be shared across multiple screens, with Windows 8.1 even being able to push video straight to another screen via Miracast.

Bing features heavily and is built into nearly every app, most of which have been given a refresh. Office and Mail are the most significant of the redesign, although everything from the Calendar, to a clever cooking app, have been tweaked.

Xbox Music takes on a new appearance with Windows 8.1, although it is only slight. The app now makes it easier to access your music collection quickly, yet takes on the same stripped-back Modern UI look it had in previous versions.

Finally Microsoft has streamlined the way that apps update. No longer is there a need to navigate to the app store, with Windows 8.1 updating automatically. 

All in all, it's a great set of changes. The big talking point is obviously the slight u-turn on Modern UI. Those who consider themselves Windows power users will no doubt enjoy the customisation they can now give to their system, but it's good to see Microsoft still pursuing the Modern UI concept.