If you want to run the new Windows 8 Release Preview on a virtual machine–so that you don’t mess up your main Windows machine, or in case your main machine isn’t a Windows box–you can run it VMWare Fusion 4.1.2 (unofficially) or the latest version of VirtualBox (officially).

For VMWare Fusion, I found this link helpful:

http://www.lifeintech.com/blog/2012/6/1/installing-the-windows-8-release-preview.html

For VirtualBox, I just downloaded the latest version, and it supports Windows 8 (32- and 64-bit) automatically. Enjoy!