http://www.dedoimedo.com/computers/virtualbox-convert.html"And vice versa. This is definitely something you may want to do if you happen to be a virtualization fan and you're running both VirtualBox and one of VMware products. The reasons for conversion could be many, including the need to preserve a license or a machine state, run it in different software for compatibility testing and who knows what other reasons virtualization geeks may have. "See link above for full article.Conversion method 1: VBoxManage
We have used VBoxManage to clone VirtualBox disks. The method here is identical, except that we will be converting to a different disk format. Let's see how this is done.VBoxManage clonehd source.vdi target.vmdk --format VMDK
Where source is your VirtualBox disk, target is your VMware disk and --format VMDK is the desired output format. Similarly, you can go the other way around, using VMDK as your source and VDI as your target. Make sure to specify the right disk format. VBoxManage clonehd function supports other formats as well.