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.