How to unmount a mounted image

I have a RAM disk that is mounted on boot that also has an image mounted to it. How should I be unmounting the image from this RAM disk?

At the main window, when I go to the top menu tabs and select Image, 3 options appear: Create Image..., Mount Image..., and Unmount Image...
I select Unmount Image... and a dialog box appears that should have a list of mounted images. But, there isn't a single mounted image listed. So how do I unmount my image?

Also, when I try to save the image via the icon toolbar, it says: "Saving image failed. Win32 error code = 32 The Process cannot access the file because it is being used by another process."

It is not possible to detach an image file from a mounted RAM disk. If you want to unmount and close the image file, first you will need to unmount the RAM disk this image is linked to, then remove the image file link in the RAM disk's properties, and then you can close/move/remove/delete the image file.

Regarding the list of mounted image files, it is important to know that image files can also be mounted as regular disks. This is normally done for populating the image with the files and folders you want to have there when you later use that image as a base for a RAM disk. If you don't have any images mounted as regular disks, the list will be empty. Please see this user manual page about image files for more information.

About this error, The Process cannot access the file because it is being used by another process, it normally indicates that the image file is open somewhere else. It's usually an antivirus program scanning it for viruses or a cloud back up program trying to upload it. You can use this tool to check what process keeps the image file open.