The most common reason to delete a disk is when you no longer want to use a particular VM and you wish to delete all files associated with it. In particular, you will want to reclaim the disk space used by the virtual disk file.

To delete a virtual disk, use the host operating system file command to remove or delete the file. (Make sure the VM is powered off first.)

If you delete the last or only disk for a VM, that VM is essentially deleted. You cannot reuse it unless you define a new disk and re-install a guest operating system. You cannot recreate the information on that disk unless you have used a system backup utility that you can use to restore the information.