http://stackoverflow.com/questions/11659005/how-to-resize-a-virtualbox-vmdk-file
C:\Users\mruckman\VirtualBox VMs\Ubuntu-12.04-64-bit-16Gig-WINT-MLR\
Ubuntu-12.04-64-bit-16Gig-WCS-DEMO-disk1.vmdk
"C:\Program Files\Oracle\VirtualBox\VBoxManage" clonehd "Ubuntu-12.04-64-bit-16Gig-WCS-DEMO-disk1.vmdk" "cloned.vdi" --format vdi
"C:\Program Files\Oracle\VirtualBox\VBoxManage" modifyhd "cloned.vdi" --resize 51200
"C:\Program Files\Oracle\VirtualBox\VBoxManage" clonehd "cloned.vdi" "Ubuntu-12.04-64-bit-50Gig-WINT-MLR-disk1.vmdk" --format vmdk
Then you need to use gParted for LiveCD