Because I have been doing graphic design work for a long time, a lot of folks ask me how to get started learning how to work with images. They wonder, should they buy Photoshop? Should they buy Corel Draw? My advice is save your money for a while and learn a little more, so you can make a good decision. Software is expensive, so spend some time playing with the programs that come with Windows, such as Paint and Imaging first. You'll better appreciate all the cool stuff Photoshop can do when you've used something that just has the "basics" first.
For example, the Imaging program introduces you to a few important concepts. To start Imaging, choose Start|Programs|Accessories|Imaging. To create your first file, choose File|New. A little dialog box pops up with options you can choose. Here you encounter your first lesson on images: file formats. You can choose from TIFF (Tagged Image File Format), BMP (bit map), or AWD (Windows fax format). For pictures, you'll want to choose BMP or TIFF, which can be used in virtually any other image editing program later.
In the Color tab, you can choose from black and white all the way up to 24-bit True color. You also need to make choices about Resolution, Compression, and Size. All of these choices affect how large your file will end up. One of the most misunderstood aspects of working with images is that size does matter. Create your images only at the resolution you need. If you are never going to use the image anywhere but on screen (such as a Web site) it doesn't have to be more than 72 dots per inch. Remember that the higher the resolution and the more colors it uses, the larger the image file.
Once you've made your choices, you encounter the Imaging interface. You see the drawing tools on the bottom toolbar. If you've never used drawing tools before, these simple ones are a great way to start. For example, to draw a line, you click the Straight line tool and click and drag the pointer. If you want to move or resize your line, you click the Arrow (selection) tool and click. The pointer changes to a four-pointed arrow, so you can drag the line to a new location. If you want to change the length of the line, click the square "handle" at the end of the line and drag. If you want to change the color or width of the line, you right click it and choose Properties.
The other tools in the Imaging program work similarly and, more importantly, work much like the tools you'd find in expensive programs. Starting small and figuring out all that clicking and dragging is a good first step toward later artistic achievements.