Here is the easy steps Convert VirtualBox (vdi) hard drive image to VMWare (vmdk) format. Have a look..
http://mikebeach.org/2011/04/18/convert-virtualbox-vdi-hard-drive-image-to-vmware-vmdk-format/
http://dossy.org/2008/05/migrating-from-virtualbox-to-vmware/
http://www.ubuntugeek.com/howto-convert-vmware-image-to-virtualbox-image.html
Cheers, Yours Udin 