I faced a problem while trying to test the new release of Moblin (2.1) which is an OS primarily designed for netbooks. When trying to boot from the live image, I get an error message stating that the kernel is not supported and that I must have something called "pae" enabled, I googled around and found what "pae" is, it's a feature in the processor and is an abbreviation for "Physical Address Extension" and here is a brief description (not quite good though) http://wiki.answers.com/Q/What_is_pae, anyway here are the steps I used to get this .img file running in my virtualbox:
Download the .img file from the website
Rename it to .iso
Assign it in the storage (as a virtual ISO CD)
Open the options for the virtual machine you've just created
Click system -> Processor -> Enable PAE.
Now you can run it and continue with the live image or installation.