For many attempting to upgrade to Windows 10’s official build 10162, the upgrade is failing at 40%. If you try to upgrade, you’ll get this issue. However, a clean install is working properly. After initiating the update, it’ll reboot to the installation screen and fail with an error asking you to revert to previous windows. Once you revert, you’ll be welcomed with something like this:
Also, attempting upgrade from within Windows 8x, you’ll run into an error like so:
The reason is the selection of a particular component on existing Windows 8.1/10 installation: Microsoft .Net Framework 3.5.
If you have Microsoft .Net Framework 3.5 enabled in Windows Features, you will not be able to proceed with the upgrade. This feature is either enabled by you or by some application that you installed. For me, I enabled it as I’m a developer. Also, applications like Paint.Net requires this framework. Similarly, games like Elite Dangerous requires it as well. Bottom line: there is a very good chance you will have Microsoft .Net Framework 3.5 enables one way or another.
You need to uncheck it in order to proceed with upgrade of Windows 10 Build 10162. You can access the “Windows Features” by searching (type it:) windows features while start menu is open or you can go to Control Panel -> Program and Features -> Turn Windows features on or off
If you turn it off, you might get a warning. Ignore that and continue with upgrading to Windows 10 Build 10162. You can open a downloaded ISO file and run setup. Or you can get the update from windows update. Either way, it’ll succeed.