How to Change UUID in Virtual Box

For example, you have a virtual hardisk in  D:/VirtualAX/virtualdisk.vmdk

If you got the following error when trying to mount a copy of a vmdk file.
A hard disk with UUID {55b773b8-cbcb-42ea-9a44-1368b30ed823} or with the same properties ('D:/VirtualAX/virtualdisk.vmdk') is already registered.

The solution for that error, you must change UUID of this file. This is the way :

From the command prompt, go to directory where you install Virtual Box like this picture :
 

then write this code :

VBoxManage internalcommands sethduuid D:/VirtualAX/virtualdisk.vmdk

then pres Enter in keyboard.

Now, your virtual hardisk have a new UUID.