Symptom
An alert box with this message appears when you try to delete a disk image file:
"This operation cannot be completed because the item <name of disk image file> is in use."
Solution
This is a normal behavior. You only need to quit using files stored on the disk image to be able to delete it. You make a disk image appear on the desktop or otherwise become available by double-clicking a ".img" file. This is sometimes called a "mounted" disk image. Though a disk image is not actually a disk, it behaves as one. Follow these steps to put it way or "unmount" it:
1. Find the related disk image on the desktop or in the Finder. It has the same name as the item you are unable to delete, but without the ".img" or ".dmg" filename suffix. It has a disk icon, and it appears in the Computer list in the Finder window.
2. Select the disk image that appears on the desktop.
3. Choose Eject from the File menu, or drag it to the Trash. If the symptom message appears again, close any files or applications that you opened from the disk image. If you cannot determine which are in use, quit all running applications or restart the computer.
For more information on disk images, see technical document 106161: "
Mac OS X: About Using Disk Copy Images".