Looking to build a PC for Gaming and Art/Photoshop: Need Help

I've never built a computer before and I quite honestly don't know the first thing to do. I have looked threw your guides again and again and they are still to confusing for me. I get overly frustrated because I can't understand anything. People have told me building a computer is cheaper then purchasing one so here I am.

I don't have a lot of money and the highest I can go is about $600 or so. Need help or ideas on what I should get. Again I have tried to understand your guides but they are still way to confusing. At the moment I have a Dell 8400 with I believe 1GB RAM and a ATI-Radeon X1650 PCI Express Card. That's all I know about my computer, also it's a 32bit Processor.

Please, anyone could I please get some sort of help?

Also I have no idea where to post this question, to many options and I don't know exactly were I should had posted it. I saw 'Tom's Guide' and thought this would have been the closes thing to what I need.

Thank You in advance.