Yesterday Microsoft released Windows 10 build 16199 for Windows Insiders. As it is a Fast Ring, official ISO images are not available. Here is how you can download ISO images to install this build from scratch.
To download Windows 10 Build 16199 ISO images, do the following.
Point your browser to the following link:
There, you will see the following list of files:
To download the 64-bit English version of the OS, click on the link "16199.1000.170513-2252.RS_PRERELEASE_CLIENTCOMBINED_UUP_X64FRE_EN-US.ISO"
To download the 32-bit English version of the OS, click on the link "16199.1000.170513-2252.RS_PRERELEASE_CLIENTCOMBINED_UUP_X86FRE_EN-US.ISO"
Note: These ISO images are not official. You should use ANY unofficial/third party ISO images for testing purposes only, i.e. in a Virtual Machine. Images there provided by Wzor.
That's it. Now you can install Windows 10 build 16199 from scratch.