As you probably heard, there are two build numbers around the Internet for Windows Phone 7 NoDo: 7389 and 7390. Build 7389 was leaked on the Internet some time ago and some used it to debrand their T-Mobile HD7.
While already running Windows Phone 7 NoDo build 7389, a user received an update notification for the March update, which is, of course, NoDo. After applying the update, he was presented with Windows Phone 7 NoDo build 7390. This is normal from several points of view: 1. the initial leaked NoDo was not the final version to be rolled-out and 2. 7390 — besides being final — is the one the device has been flagged for as it has a higher build number. Check out the video below: