Virtual Box Snake

I booted up my trusty VirtualBox virtual machine today, to write out an invoice in some crusty rusty old PC accounting software (proprietary, dropped by developer, no longer supported, but that's another story). I was heartily informed that VirtualBox 3 is available. Wooters.

But when I went to install/upgrade the .deb package, I had the unfortunate error:

Error: Conflicts with the installed package 'virtualbox-2.2'

Now, I don't know much about anything, least of all virtual machines. But I was wondering... could I install a virtual machine inside a virtual machine?!? That way obviating the need to trash my precious working version of VirtualBox 2?!?! A cunning plan, worthy of Baldrick himself.