There are a number of options for getting your hands dirty with the new Windows 8. Naeem has a great setup script for dual-booting, but I decided to try setting up a virtual machine. I have a number of choices for the hypervisor:
To set up the VM in Virtual Box, click the New button from the toolbar. In the wizard, choose a name for your VM and then choose WinXP x64 as the OS:

On the next screen, make sure you give the VM more RAM than the miserable default of 192MB:

Then you need to setup the details for a new virtual hard disk:

The rest of the screens in wizard are pretty straightforward. Once you have your VM setup, you need to connect it to the downloaded Windows 8 ISO. You do this by opening the settings screen for the VM and clicking the CD icon (took me a while to work this step out):

Then on the popup menu, click “Choose a virtual CD/DVD file” and browse to the ISO image for the Windows 8 developer preview.

Now you are good to go! Start your virtual machine and it will launch you straight into the Windows 8 installation process. Hurray!
But what’s it like to use Windows 8 on a VM?
To be honest, it’s not the best experience out there. Simple things like moving the mouse around are noticeably laggy … it’s unlikely to be my laptop since I’m on a Core i7 machine with 8GB RAM. Also, Windows 8 does not seem to get correctly informed of the screen resolution. This results in the reserved 1 pixel strip being impossible to hit. Boo!
These performances issues do not occur if you boot the OS on the machine directly, so I’m pretty sure it’s a consequence of the virtualisation.
Having said this, it’s better than nothing. If dual boot or a dedicated machine are not options for you, then a VM will allow you to have a sandpit for playing with some of the new tech from Microsoft. Enjoy!