C:\Program Files\Oracle\VirtualBox> .\vboxmanage list hdds | more
Delete those motherfuckers:
C:\Program Files\Oracle\VirtualBox> .\vboxmanage closemedium disk 5dc7f9f9-74a1-4e28-b2a4-ccd0cb3a7d25
To assign a UUID discovered in the error message when trying to start a VM or assign an HD to a VM:
C:\Program Files\Oracle\VirtualBox> VBoxManage internalcommands sethduuid "G:\VirtualBox VMs\VERITAS_VAR.vdi" 000607c1-b714-4e4f-90d0-e9d91e67edda