Windows 10 build 10074

Windows 10 build 10074 is the first released Insider Preview build and one of the earliest Insider Preview builds. It was released to Insiders on 2015-04-29 from Microsoft. This build contains the new flat icons.

Cortana

 * Start and Cortana are now more tightly integrated
 * New experiences in Cortana powered by Bing Instant Answers

Music and Video Preview Apps

 * Music app is more immersive with a true full screen mode
 * You can download movies, TV shows and TV seasons with the Video Preview app on up to three devices

Other

 * Closing an application in Tablet Mode takes you to the start screen now
 * Multi-tasking improvements - Alt+Tab, Task-View, Snap Assist
 * Windows Store has been expanded to 41 more markets
 * Windows Store is now a blue tile instead of grey