If you’ve ever dual-booted a machine before, this shouldn’t seem too foreign. All you need to do is create a new partition for Windows 8, install it on that partition, and then edit your new boot menu so Windows 7 stays the default OS. Here’s how to do it.
Step One: Create a New Partition
Find your hard disk in the graphical list that appears in the bottom pane. Right-click on it and hit “Shrink Volume”. Shrink it down so you have at least 20GB of space left on the end of the drive, and hit OK. Then, click on the “Unallocated” block of that drive that appears and hit “New Simple Volume”. Hit Next on the next few windows until you get to the “Format Partition” window. Here, give it a volume label you’ll recognise (like “Windows 8”) and hit Next. It should format the drive for you. Now you’re all set to install Windows 8.
Step Two: Install Windows 8
If you haven’t downloaded the Developer Preview ISO yet, head over to the Windows Developer Center and download it. Burn it onto a DVD using something like ImgBurn, or burn it to a thumb drive if you don’t have a DVD drive in your machine. Make sure your computer is set to boot from CD or USB, stick in your installation media, and reboot.
On the next screen, find your new partition on the list of drives. Make sure it’s the right one, because you’re about to write over whatever’s on it. Hit “Next” and let the installer do its thing. When you’re done, your computer should reboot into Windows 8. It’ll probably reboot one more time after it does, then you’ll be greeted with the Windows 8 Start screen. If you choose to enter a Windows Live ID here, make sure you have access to your email and can confirm your computer — otherwise it might not let you boot into it.
Step Three: Make Windows 7 the Default (Optional)
On the boot menu, click on the button at the bottom that says “Change Defaults or Choose Other Options”, and hit “Choose the Default Operating System”. From there, you can pick Windows 7 from the menu. From now on, your computer will boot into Windows 7 by default, but if you feel like playing around with Windows 8 that day, you can just pick it from the boot menu. Enjoy playing with the developer preview, and let us know what you think in the comments.