Put an existing machine into a VirtualBox
- Convert an existing computer to VMware Player appliance
- Convert VMware Player to VirtualBox appliance
- Import the appliance into VirtualBox
Convert an existing computer to VMware Player appliance
Use VMware’s free tool VMware vCenter Converter to convert both Windows and Linux physical machines into VMware virtual machines. You could boot the result in the free VMware Player application.
Download vCenter Converter from VMware and launch it on the computer you want to turn into a virtual machine. Click the “Convert machine” button on the toolbar and select the current, powered-on computer as the source. Choose a VMware Workstation, VMware Player, or VMware Fusion virtual machine as the destination and configure the options for the virtual machine.
The utility will then create a virtual machine from the current Windows system, modifying it so it will boot properly in a virtual machine program. Save that virtual machine to an external hard drive and boot it up on a different computer.
Convert VMware Player to VirtualBox appliance
Feb 2016
https://www.maketecheasier.com/convert-virtual-machines-vmware-virtualbox/
To migrate from VMware to VirtualBox, you first need to export the VM in an .ovf file.
Oct 2012 — so might not be relevant today but a fair warning
http://www.howtogeek.com/125640/how-to-convert-virtual-machines-between-virtualbox-and-vmware/
VirtualBox and VMware use different virtual machine formats, but each supports the standard Open Virtualization Format. Convert your existing virtual machine to OVF or OVA and you’ll be able to import it into another virtual machine program.
Unfortunately, this may not always work perfectly, as VirtualBox and VMware both seem to use slightly different OVA/OVF implementations that aren’t entirely compatible. If this doesn’t work, you may want to reinstall your virtual machine’s guest operating system from scratch.