As expected, Microsoft has flipped the switch on the first major update to Windows 8.1, bringing a series of changes and tweaks designed to improve the operating system's non-touch experience for mouse and keyboard users.

The update, which arrives as part of April's Patch Tuesday, is formally known as Windows 8.1 Update (previously Update 1 or Spring Update) and will be mandatory to all Windows 8.1 users. In fact, those that decline the update won't receive any further patches beyond May 13, 2014.

So, Windows 8.1 RTM has essentially reached End-of-Life early and Windows 8.1 Update is the new servicing baseline for Windows 8.1 – Windows 8 will still get security updates. The reason behind the move is unclear but enterprise customers in the midst of a Windows 8.1 rollout will need to get busy.

In any case keyboard and mouse users will likely want to get this update as soon as possible. Among the changes, Windows is finally becoming contextually aware, meaning if you are on a PC without a touchscreen it will now boot directly to the desktop by default, while touch-enabled laptop or tablets will boot to Metro. Users can still manually configure this too.

Microsoft is also making the default program for pictures and audio files relevant to the device they are being opened on. Whereas it used to be that these files were associated with the Metro-style Photo and Music apps (a big annoyance), pictures and audio files now open by default in the Windows Photo Viewer or Windows Media Player if opened from a non-touch PC.

The update will bring dedicated power and search buttons to the Start screen, new right-click context menus for desktop users, and the ability to pin Modern apps to the taskbar. Inside Modern apps, you'll now find a title bar and the taskbar if you hover your mouse to either the top or bottom of the screen, making it easier to switch between and close Modern apps.

Once again these changes will only be apparent, or enabled by default, on PCs.

You can grab the latest bits from Windows Update as usual or download it directly from right here. Windows 8.1 Update arrives on the same day Microsoft is bidding adieu to Windows XP support with one final round of security patches.