Tools > Options > Warnings 1

Missing file from project - Warn when opening a project and a media file cannot be found anymore.

Overwriting output file - Ask for confirmation when overwriting media files and projects. If unchecked there will be no warnings before you (accidentally or deliberately) overwrite an existing file.

Starting a new project - Ask whether to discard current project before starting a new session.

Removing audio or video files from the list - Ask for confirmation when removing video or audio files in the main window.

Removing video filters from the list - Require a confirmation when deleting video filters from the list.

Video and audio lengths are different - Warn when audio and video don't have equal length.

Output codec or format has been changed or reset - Warn when changing output resolution or color depth causes the codec to be changed (because the selected codec didn't support these parameters)

Regularly check for updates - VideoMach should inform you when a new version is released.