Not everyone is able to make the financial investment for Photoshop and there are others who do not need (or require) all the things that programs like Photoshop can do.
So here are some alternatives that will cost you nothing, nada, zip, zero, zilch, goose egg:
1. Gimp. "GIMP is an acronym for GNU Image Manipulation Program. It is a freely distributed program for such tasks as photo retouching, image composition and image authoring." Here is an introduction page, and here is a tutorial page so you can take a look at what it can do.
2. Fotografix. "While graphic design professionals probably wouldn't be able to substitute Fotografix for Photoshop, it's certainly a capable free alternative for the average Joe."
3. Paint.NET. "Paint.NET is free image and photo editing software for computers that run Windows." You will find the features list here, and tutorials here.
4. Photoscape. "Photoscape is the fun and easy photo editing software that enables you to fix and enhance photos." You can take a look at some screenshots here.
5. Adobe Photoshop Online. The title pretty much says it all, and you can take a test drive here.
(The screen shots below are from my computer not promotional broo ha ha so you have a real world idea of what they truly look like and what some of the options and features are and you can click on either image to view larger and in a new window.)
6. FastStone Image Viewer. From their website: "a fast, stable, user-friendly image browser, converter and editor. It has a nice array of features that include image viewing, management, comparison, red-eye removal, emailing, resizing, cropping and color adjustments. Its innovative but intuitive full-screen mode provides quick access to EXIF information, thumbnail browser and major functionalities via hidden toolbars that pop up when your mouse touches the four edges of the screen. Other features include a high quality magnifier and a musical slideshow with 150+ transitional effects, as well as lossless JPEG transitions, drop shadow effects, image annotation, scanner support, histogram and much more."
7. IrfanView. "IrfanView is a very fast, small, compact and innovative graphic viewer for Windows. It is simple for beginners and powerful for professionals. It has created new and/or interesting features in its own way and is the first Windows graphic viewer WORLDWIDE with Multiple (animated) GIF support."
It really does have a bunch of features, too numerous to list here.
If you know of any no cost Photoshop alternatives that I have not listed here, please let me know and I will be sure to post them.