If mounted as drive: right-click drive letter → "Dismount". Failure to dismount leaves a stale device node, which can cause Windows to bluescreen on next backup attempt (rare, but known).
You don't need to search for a separate "Acronis Image Viewer" download. The tool is already in your hands. By the image, you transform a static, heavy backup file into a browsable virtual drive. It saves time, saves storage space, and gives you instant access to the data that matters most. acronis image viewer
But you don't want to restore the entire backup just to get that one file. If mounted as drive: right-click drive letter → "Dismount"