From the Supersite:
f you want to experiment with Windows 8 without having to sacrifice a physical system, you can boot Windows 8 from a Virtual Hard Disk (VHD) in Windows 7. Although you could use Hyper-V, I believe it's better to use real hardware to see how Windows 8 interacts with drivers.
Creating a virtual drive:
Beginning with Windows 7, you can now mount VHDs exactly like a physical disk. By mounting a VHD, you can easily copy files to and from the virtual disk
In case anyone needs it, to run disk management:
To run Command Prompt as an administrator
Click the Start button .
In the search box, type "command prompt".
In the list of results, right-click Command Prompt, and then click Run as administrator. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
Open the Disk Management console by typing diskmgmt.msc at an elevated command prompt.