Background Preview Generation - This preference determines when miDVD generates movies for viewing when previewing your DVD.
When selected, miDVD generates previews in the background while you are doing other tasks in miDVD. This means that when you switch to preview your DVD, the preview will display more quickly. However, on less powerful computers this setting may affect your computer's overall performance.
When not selected, miDVD only generates movie previews once you select Preview mode. This means your preview will take longer to load, but your computer's overall performance will be unaffected by preview generation.