If you've outgrown the Microsoft Paint program that's bundled for free with Windows, but you don't want the complexity or expense of a professional tools such as Photoshop, there are plenty of free programs that will fit the bill.
One that's recently come to my attention is Chasys Draw IES. It''s an image editor, icon editor, file converter, image viewer, and hugely powerful drawing/painting program, all in a single app.
As you can see from the screen shot below, there's a good collection of brushes, effects, tools and features. You can even install it as a portable app to a USB stick.
Perhaps the most novel feature is the animation capability. Create a picture then click the Animation menu to create a frame. Move something in the picture, then create another frame. Continue the process to build your movie, then save it as an AVI file. It's just like traditional stop-frame animation, without the need for cameras or any model-making skills.
Chasys Draw is a 16 MB download for Windows, from http://www.jpchacha.com/chasysdraw/index.php and is completey free of charge. According to VirusTotal and my copy of Avast, it's also free of malware and viruses.