Microsoft says that if you don’t keep up with the Windows 10 Technical Preview updates your computer could soon stop booting. On a response at the Microsoft forums, one of the support engineer for the company explains that each preview build of Windows 10 has an expiration date.
The Microsoft engineer explains that approximately two weeks before a build’s license expires, you will start receiving warnings that the preview will expire and that you should consider updating to the latest build.
After the license expires, your PC will automatically reboot every three hours. Two weeks after the license has expired Windows 10 will not boot any longer.
Here is the list with dates:
If you’ve been trying to update, but everything has failed, it’s probably because something is wrong with Windows Update. The easiest way to resolve this issue is for you download the ISO file for the latest build of Windows 10 and try upgrading your system.
If your computer is no longer booting because of an expired license, you’ll need to download the latest ISO version of Windows 10 Technical Preview to another computer and you’ll need to create a bootable media to upgrade your system.
Source Microsoft