RB Mods shows you how you can test Windows 8 Release Preview in a virtual environment using Oracle's Virtual Box, you can learn it over here.
With the advent of desktop virtualization becoming more mainstream, it gives the computer enthusiasts and IT professional to test different operating systems easily. One product that is used quite often is Oracles Virtual Box. Virtual box is an open source type 2 hyper-visor that uses the host's resources to run a virtual machine in an isolated environment. This gives the ability to test beta and release candidate operating systems without impacting your production workstation.