How can I get into graphic design?

I see all these icons that people produce - for example Apple's icons - and I think to myself, why can't I make things like that?

Right now, I have a Dell Inspiron 17R. Not exactly the most powerful machine in the world, but it does the job. I also have an iPad 2. What I'm wondering is, are there any apps for either of these that are relatively inexpensive that I can use for graphic design?

Also, I need some tutorials in how to get started in graphic design. I have downloaded basic graphic design software in the past - for example GIMP - however I haven't really known where to get started. I'm sure some of you must be graphic designers, so do you have any tips and tutorials for me?

Thank you ever so much,

Tom.