I have purchased several new Memory Cards for my Nikon Coolpix L820 35mm Camera and, still have the same issues - the cards download some of the photos BUT not all of the photos. There are also some sort of files that I don't recognize and, won't let me delete from the Memory Card, which then has resulted in my having to purchase a New Memory Card once again. I tried the Compressed Air Can idea and, am unsure if this will take care of the problem or not. Please help. Thank you.