Microsoft is working on a big new update to its Windows 8 operating system that will launch in a special preview version at the end of June. It's called Windows 8.1.

According to a leaked screenshot of the update obtained by Paul Thurrott, Windows 8.1 will bring back the Start button, which was removed from the first version of Windows 8 in favor of a tile-based menu designed for touchscreen computers and tablets.

But Microsoft confused a lot of people with the change, even though you could switch back the regular desktop mode from the new Start menu. It's long been rumored that Microsoft would bring back the old Start button in Windows 8.1 along with an option to let users boot their PCs in regular desktop mode by default.

According to ZDNet, the new Start button won't pull up the classic-looking list of options from older versions of Windows. Instead, it'll take you to the "All Apps" screen that lists all of the apps installed on your computer or tablet.

Now we have some concrete proof that's happening. We'll likely get a full rundown of Windows 8.1 at Microsoft's Build developers conference on June 26.

Here's the screenshot. It looks like the new Start button will be a clean-looking Windows logo: