Here is briefly explained how to migrate from VMware to VirtualBox OSE (OpenSourceEdition) while preserving your virtual disks:

method 1

VBoxManage convertfromraw --format vmdk --variant Standard /tmp/debian.vmdk debian.vdi

method 2

Start Virtualbox
click File -> Virtual Media Manager
Click on the “Add” button.
Locate and select the VMware .vmdk file you’d like to convert.
Create a new virtual machine profile, selecting your imported image for the storage.
Boot your new virtual machine.

method 3

for this method to work we need to use a third party tool, qemu. Notice that VMware is not compatible to run alongwith the kernel modules provided by this tool.

sudo apt-get install qemu

We’ll use qemu to convert a .vmdk (VMware disk) to a .bin one, which can then be converted to a Virtualbox native .vdi format.

 qemu-img convert original.vmdk converted.bin

You’ll then need to use the VBoxManage utility that comes with Virtualbox to convert the .bin to a native .vdi format:

VBoxManage convertdd converted.bin converted.vdi

You can now create your new Virtualbox machine profile, using this new .vdi file as your disk image.

Migrating Windows from one virtualization solution to another is not as easy as here is described, for the same reason migrating the same windows setup from a computer to another is a pretty annoying thing. Not only for the system activation that would trigger again but also because you would have to take care of the issues covered in the following guide: www.virtualbox.org/wiki/Migrate_Windows