How to download and install Windows 10 Insider Preview for free

We’re getting close: Microsoft has been issuing new Windows 10 Insider Preview builds on a regular basis, ahead of the official release July 29th. Want to try it out? There are 64-bit and 32-bit versions available for US and UK English, Chinese, and Brazilian Portuguese, among other languages. Follow these instructions to download and install the Windows 10 Insider Preview.

Be prepared

As always with beta and preview software, you shouldn’t install it unless you’re fully prepared. This means you should back up any important files, and ideally you should have a separate hard drive or partition to install the Insider Preview on. You cannot revert from Windows 10 Insider Preview to Windows 7 or Windows 8; if you have second thoughts, you will have to reinstall from scratch.

Download the Windows 10 Insider Preview

To begin, head on over to preview.windows.com and join the Windows Insider Program. This only takes a few clicks if you already have a Microsoft account.
You then need to download the appropriate installation file (an ISO) for your system. This is probably the 64-bit (x64) version — though if you have an older system, or you want to test out the 32-bit version, grab the 32-bit download instead. The download will probably take quite a while: the 64-bit ISO comes in at just under 4GB. Note down your license key (though you will be able to visit the page later, too). Microsoft has greatly simplified the process; you can grab it from the company’s dedicated Windows 10 Insider Preview download page.
With the ISO fully downloaded, you then need to transfer it to either a USB thumb drive (preferred) or burn it to a DVD. If you have Windows 8 or 8.1, burning a DVD is fairly easy — you can do it directly in Explorer. For burning an ISO image to a USB thumb drive, the Windows 7 USB/DVD Download Tool is probably still your best bet, and we’ve also had good luck with Rufus.
If you want to install a fresh version of Windows 10 Insider Preview, reboot your computer, boot from the USB stick/DVD drive, and follow the on-screen prompts  (use “Advanced” mode when prompted). If you want to upgrade an existing version of Windows 7 or 8/8.1, just run setup.exe from the USB/DVD drive from Explorer.

Caveats and other options

You can upgrade your existing Windows 7 or Windows 8/8.1 installation to the Windows 10 Insider Preview. I would advise you to do a clean installation of the Insider Preview, however, on a separate partition or hard drive, in case something messes up. Eventually, each Insider Preview license expires, but not before another Preview build is released. Other potential caveats/pitfalls can be found on the Windows 10 Insider Preview FAQ.