If you want to run the Advanced PICK "as is" in a virtual machine, I'd strongly recommend using VMWare Workstation instead of VirtualBox or a similar tool. Advanced PICK was pretty stable as far as the way that it interfaced with the hardware, but many of the third party add-ons were "interesting" in their behaviors.
It is relaitvely safe and easy to pop in a VMWare CD and p2v an Advanced PICK machine. It is relatively difficult to get a complete and stable image using VirtualBox. The worst part is that I've had cases where an image seemed to be fine until I got to some specific point such as year or quarter end, or EDI interface, etc... Unless you have the time and resources to test exhaustively enough to bet your business on it, I'd take the conservative approach.
-PatP