Step 1. Download the WindowsDeveloperPreview-64bit-English-Developer.ISO as mentioned here Or if you have a x86 processor opt for the x86 version.
Step 3. Select ‘Typical configuration’ and click next.
Step 4. Select ‘I will install operating system later’ and click next
Step 5. On the next screen, select Microsoft Windows as the Guest Operating System, choose Windows 7 from the version drop down (windows 7 x64) if you downloaded the 64bit ISO.
Step 6. Give your virtual machine a name and specify where you want to save the image, ensure you have at least 20Gb free disk space available.
Step 7. On the next screen select ‘Store virtual disc as a single file’ and adjust the maximum disk size to 20Gb
Step 8. Click finish
Step 9. Now we are ready to install Windows 8, click ‘Power on this virtual machine from the menu
Step 10. Click the VM file menu followed by Removable Devices, CD/DVD (IDE), and click Settings.
Step 11. Select ‘Use ISO image file’ and click browse, now navigate to and select the WindowsDeveloperPreview-64bit-English-Developer.ISO you downloaded in step 1.
Step 12. Press CTRL + R to reset the virtual machine
The Windows 8 installation process will now start. Follow the on screen prompts to install Windows 8 Beta Preview.