Just a note for beginners: An important distinction between a viewer like Irfanview and an editor like GIMP or Paint.NET is that in the former, the emphasis is on speed and lightweightness, so you just execute an image file, and it appears on screen, and you press a key to advance to the next image in the folder or backtrack to the previous image in the folder, or another key to quit. An editor is a larger program that you open, which typically takes longer to do, and can open several files in multiple little windows within the main program, but there's no functionality to quickly move through the folders, and is rather intended for modifying the textures. I use Photoshop for that purpose, which is similar to GIMP and Paint.NET.