I've seen people on the net offering images of a particular Linux setup, and they offer it as either VMDK/VMX files or ISO files. Now an ISO seems to work with VirtualBox, because I can tell it to mount a CD/DVD drive and use the ISO instead of a physical drive, but the VMDK and VMX files are always listed as being for use with VMWare/VirtualBox.
So how do I use those files with VirtualBox? When I try the Appliance Import Wizard it tells me it only deals with OVF files.
(I'm using Sun VirtualBox 3.0.4)
VMDK/VMX are VMWare file formats but you can use it with VirtualBox:
Actually, for the configuration of the machine, just open the .vmx file with a text editor (e.g. notepad, gedit, etc.). You will be able to see the OS type, memsize, ethernet.connectionType, and other settings. Then when you make your machine, just look in the text editor for the corresponding settings. When it asks for the disk, select the .vmdk disk as mentioned above.