You cannot create disc image using Astroburn Lite. This functionality was not provided in Lite version. You may use Astroburn 1.0.91 (download from Software for burning, grabbing and mastering CD, DVD, HD DVD and Blu-ray discs ::

In Astroburn Lite you can only burn files or images. You will get full functionality in Astroburn Pro 1.1.0, which will be released soon. Watch for announcements!