There's also:
MyPaint - Free download and software reviews - CNET Download.com or
Paint.NET - Free download and software reviews - CNET Download.com
MyPaint - Free download and software reviews - CNET Download.com (a little more advanced I thought)
They are all small programs and are free.
Try them each out and if you don't get into the swing of things try another one.
It should be fun and intuitive.