I've found hacking game hackxor, but it's made for vmware.
I don't have any experience with vmware and I don't want to install it in my machine.
So I'd like to run hackxor inside VirtualBox if it is possible.
I did not download it and not sure if this is everything but you should be able to get started with it. The most important part is that you are able to use the provided disk image.
VirtualBox supports vmdk (Vmwares image format) out of the box. So you should be able to directly use the provided disk image with VirtualBox. If this does not work have a look at the VirtualBox manual.
If this does not work you can also convert the disk image with