HOW TO: WINDOWS 10 INSIDER PREVIEW - EVERYTHING YOU NEED TO START
Before we get too involved, it’s worth noting that the Windows 10 Insider Preview is limited to PC and Windows tablets with x86 processors—there’s no version for Windows RT tablets and their ARM processors available, as Windows RT tablets won't be receiving Windows 10. (Sorry, Surface RT owners.) If you’re unsure which version of Windows your tablet is running, right-click on the “This PC” icon in File Explorer and select Properties. Your Windows edition information will be at the top of the window that appears.
Here are Windows 10’s other hardware requirements, which are just as modest as Windows 8.1’s.
Processor : 1GHz or faster with support for PAE, NX, and SSE2
RAM : 1GB (32-bit) or 2GB (64-bit)
Hard disk space : 16GB
Graphics card : Microsoft DirectX 9 graphics device with WDDM driver
Some additional notes: You’ll also need a Microsoft account and Internet access. And if you want to access the Windows Store or use Windows Apps, your monitor’s resolution will need to be at least 1024x768. The Windows 10 Insider Preview is available in English, Chinese Simplified, and Brazilian Portuguese.
Still here? Great! Now head over to Microsoft's Get Started Portal and click the Get Started button. After registering for Windows Insider, you’ll be prompted to download the Windows 10 Insider Preview. Download the appropriate Insider Preview build for your machine—the “This PC” or “My Computer” Properties window can also tell you if you have a 32-bit or 64-bit processor under the “System type” field.
Jot down the product key for the Insider Preview, too. though I didn't need to use it to install, it couldn't hurt to have it handy.
Product key: 8N67H-M3CY9-QT7C4-2TR7M-TXYCV
Now all that's left is to double click the ISO file, Windows will mount the image automatically and allow you to begin the installation. If Windows fails to mount the ISO file you may want to try a virtual drive like DaemonTools Lite to get the job done. Installation is easy.
Once setup begins it is EXTREMELY IMPORTANT to read everything! Windows will ask you what your various installation preferences are including whether you'd like to do a fresh installation or an upgrade installation to keep your files. This is very important!
Now that you're done enjoy your new operating system! As long as you have Insider Builds turned on Windows 10 will be free for you! If you choose to stop receiving Insider Builds after the official release you can activate Windows 10 with your Windows 7, 8, or 8.1 serial number. If you don't have one you can buy a copy on the cheap at Windows.com
That's it guys, easy stuff. If you have questions please feel free to ask me! :D I've done this 20 or so times now on various machines so I have it down pretty well.
DISCLAIMER I do not work for Windows. I am an IT Professional and tinkerer. You are following an amateurs guide. You are installing the Windows 10 Insider Preview at your own risk. Though the likelihood is very low at this stage in Microsoft's development of Windows 10, I do not assume responsibility for anything horrible happening to your machine during or after this process. Please consider the consequences before installing this software.
Here's a link to a snap containing even more information.
^_^ - VoyagerXyX