If you just want to retouch images a bit, Photoshop is overkill. Check out Paint.NET, an open-source freeware editor with all the essential tools, including those for cropping, rotating, resizing, adjusting colors, and creating collages.
Paint.NET supports the most popular image formats--JPEG, PNG, GIF, TIFF, and others--but not superhigh resolution ones like RAW. However, you'll find such basic effects as Red Eye Removal, Emboss, Mosaic, and Oil Painting, and a few higher-end features such as Clone Stamp, Lasso Select, and Magic Wand. Like a full-fledged graphics package, Paint.NET even supports layers and an actions manager. The interface is very convenient, and the panels are semitransparent, so you won't need to hide them.
Version 3 fixes many old quibbles. Multiple-image editing is done through a convenient thumbnail manager in the upper-right corner of the app; blurry tool icons have been sharpened as well. Paint.NET is far better than Microsoft Paint, and given its free price, it's a no-brainer for anyone who does a lot of minor graphical tweaking.
Paint.NET is free image editing and photo manipulation software designed to be used on computers that run Windows. It supports layers, unlimited undo, special effects, and a wide variety of useful and powerful tools.