VirtualBox is a free virtualization software that works both for the 32-bit and 64-bit operating systems. Using VirtualBox you can run a virtual PC inside your existing computer, in other words, you can run any number of supported operating systems within your existing operating system. It supports a large number of operating systems including Windows, Linux, FreeDOS, FreeBSD, Mac and more.
VirtualBox creates the virtual PC storage files as VDI files on your computer. If you want to import the virtual disk files from some other software to VirtualBox, then you might want to convert them to VDI first. You can do this using the CloneVDI software. This software can also clone the VDI files by modifying their UUID and you can also modify the properties of the existing VDI files.
CloneVDI actually makes use of the command line tools that come with VirtualBox itself. It acts as the GUI front-end for the these CLI tools. You have to select a source disk image file that could be a VDI, VHD, VHDX, VMDK, or a raw disk image. The destination file is always a VDI disk image. It displays the source disk information like the partition size and the partition type.
In the options, you can choose to increase the virtual disk size or the partition size. You can compact the drive while copying its contents to the destination. If you are cloning the VDI, then you should generate a new UUID. But if you want to make a backup, then you should keep the old UUID.
When you click on the Proceed button, it simply passes all the parameters to the VBoxManage command line tool. You will see a CLI window popup and process the source disk image. Depending on the size of the disks and the tasks being performed, the process may take a short or long time.
You can download CloneVDI from https://forums.virtualbox.org/viewtopic.php?t=22422.