How to convert the disk to fixed in Virtual Box First create a disk in Virtual Machine and select the disk type. Next creating the disk as dynamically allocated. Now the command to use the convertions. Check the options, type vboxmanage /? C:\Users\User\VirtualBox VMs\win10>dir /p Directory of C:\Users\User\VirtualBox VMs\win10 15-03-2019 10:22 <DIR> . 15-03-2019 10:22 <DIR> .. 15-03-2019 10:22 2,155 win10.vbox 15-03-2019 10:22 1,666 win10.vbox-prev 15-03-2019 10:22 9,728 win10.vhd 3 File(s) 13,549 bytes 2 Dir(s) 73,797,705,728 bytes free C:\Program Files\Oracle\VirtualBox>VboxManage modifymedium "C:\Users\User\VirtualBox VMs\win10\win10.vhd" --resize 3000 0%... Progress state: VBOX_E_NOT_SUPPORTED VBoxManage.exe: error: Resize medium operation for this format is not implemented yet! C:\Program Files\Oracle\VirtualBox>VboxManage modifymedium "C:\Users\User\VirtualBox VMs\win10\win10.vhd" --resize 3500 0%... Progress state: VBOX_E_NOT_SUPPORTED VBoxManage.exe: error: Resize medium operation for this format is not implemented yet! C:\Program Files\Oracle\VirtualBox>VboxManage modifyhd "C:\Users\User\VirtualBox VMs\win10\win10.vhd" --resize 3500 0%... Progress state: VBOX_E_NOT_SUPPORTED VBoxManage.exe: error: Resize medium operation for this format is not implemented yet! Note : I was getting error when trying the command and found size need to be larger than exists. finding where the file exists and size C:\Program Files\Oracle\VirtualBox>VBoxManage.exe list hdds UUID: a2289d4b-573a-4e83-9de8-9db3246c79e4 Parent UUID: base State: created Type: normal (base) Location: C:\Users\User\VirtualBox VMs\win10\win10.vhd Storage format: VHD Capacity: 3624 MBytes Encryption: disabled C:\Program Files\Oracle\VirtualBox>VboxManage modifyhd "C:\Users\User\VirtualBox VMs\win10\win10.vhd" --resize 4500 0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100% This process will delete the original disk file from your drive. Warning: You may want to back up the original disk file if you haven’t already, just in case anything goes wrong with this process. Run the command to remove the original disk from VirtualBox’s registry and delete it. VBoxManage.exe closemedium UUID --delete VBoxManage.exe closemedium a2289d4b-573a-4e83-9de8-9db3246c79e4 --delete VBoxManage.exe closemedium a2289d4b-573a-4e83-9de8-9db3246c79e4 –delete once after rename the new disk and attach to the new disk. .