If you’re using a previous build of Windows 10, you can use the PC Settings Preview Builds interface to upgrade to Windows 10 Technical Preview 2. But anyone can download the ISO versions of this new build and perform a clean install or upgrade on the PC of their choice.
Technically, you’re supposed to be a member of the free Windows Insider program to install the latest pre-release builds of Windows 10. And while I do think you should join this program and provide Microsoft with feedback that will help shape this next Windows version, anyone can grab these ISO files and get started.
Note: Microsoft doesn’t make ISO versions of every build available for download, however, so you may need to use Windows Update in build 9926 or newer to perform future upgrades.
To grab your ISOs, head on over to the Download Windows 10 Technical Preview ISO page on the Windows web site. Here, you will find 64-bit (x64, a little under 4 GB big) and 32-bit (x86, 3.01 GB) ISO files in a variety of languages.
Be sure you grab the right one, especially if you plan to upgrade from a current install of Windows 7 or Windows 8.1; you will need a 32-bit version of Windows 10 to upgrade from a 32-bit version of Windows 7/8.1, for example.
As I noted in Microsoft Releases Windows 10 Technical Preview 2: Get It Now, you can copy this ISO to a bootable DVD disc or USB memory stick using the free Windows USB/DVD Download Tool and then upgrade or clean install as you desire. (If you’re installing in a virtual machine in Hyper-V, VirtualBox or a similar solution, you can do so with the ISO file; there’s no need to copy it to physical install media.)