VirtualBox Convert Fixed Disk to Dynamic/Stadard

How to check if you disk is Dynamically allocated storage or Fixed.

VirtualBox -> Select Instance -> Settings -> Storage -> Select Disk -> Details.

You can't do a direct conversion, but you can duplicate a new disk which is dynamic.

VBoxManage clonemedium disk "D:\fixed_disk.vdi" "D:\dynamic_disk.vdi" -variant Standard

Swap Disk

VirtualBox -> Select Instance -> Settings -> Storage -> Select Disk -> Attributes - Hard Disk -> Choose Virtual Hard Disk File.