Lots of people think using a layer mask is only for the advanced Gimp users, fortunately this isn't the case at all. Let me explain you the basic usage of layer mask on a easy to follow step-by-step example.
If you can't copy files that are bigger than 2 or 4 GB, usually HD movies and such, on to your USB key, it's usually due to the file system the USB key is formatted to.
Pretty cool Photoshop tutorial, where we will add two text layers, one will be placed behind and the main at front. And I think you might really enjoy the final result, go for it and have fun!