If your PC won't boot (corrupt boot sector, malware that destroyed the OS, or a failed hard drive), you cannot run the standard Acronis Windows app. The ISO solves this. You boot from the USB, connect your external backup drive, and tell the ISO to "Recover Entire Disk." It works even if the internal drive is completely empty.
Choose a save location and click to generate the file. Using the ISO to Create a Bootable USB acronis true image 2021iso exclusive