Hi again borate
I've discovered that if I change my laptop's power scheme to "High Power", this fixes the problem and the picture is sharp.
Your mention of the video driver got me thinking on the right lines, so many thanks for that.
I'm not clear though why VLC, WMP and other media players can display a sharp picture even when I'm using a low power scheme but Videopad's previewer can't?
By the way, my laptop is using the latest video drivers that are supported by Dell. I did try installing a later driver for my AMD controller, that I downloaded from the AMD website but it froze my machine - and then Windows wouldn't boot after that! I had to roll back Windows to the last system restore point in order to recover it, which isn't easy to do without being able to start Windows. So when you suggest to people that they check that their drivers are up to date I think you should first ask them if they are using a laptop - and if they are, I don't think you should suggest they install drivers from the chip manufacturer's website unless the laptop manufacturer definitely supports dong that.
Anyway, the original problem is fixed now, and I wouldn't have thought of changing the power scheme to "High Power" without your input. Many thanks for your help.
Dave
