Lynne Pearce

Hi. I am very new to this and am just trying to combine 3 simple videos which I recorded on my webcam. I can import them fine but when I look at 'clip preview' only the sound is playing. The videos play fine when played directly on my laptop and the thumbnails show in the Timeline but when I play the clip on Videopad I only get the audio. Am I doing something stupid? The files are all MP4. Thanks Lynne