Ok, so I'm busy making tutorials today. This is a very simple tutorial explaining exactly what each blending mode does. It's designed for Adobe Photoshop CS, but of course many of the blending modes can be found in earlier versions of Photoshop. I assume that the blending modes in PSP of the same name may work along the same lines. This by no means shows everything you can do with the different blending modes; it just explains how they work. Feel free to ask any questions you have. This may take awhile to load; it is extremely image intensive.

(Blending Modes explained)