What can I do if I got ripped off through the internet?

I did a stupid thing. I paid online for some programs that would allow me to download videos and put them on my Zune. Then after they charged my card, I couldn't get the program to work. I've since lost the website that I used (including the order number), and I emailed their "customer support" but they just return the same email over and over with basic instructions. The first program I downloaded was Ares Ultra, and it doesn't connect. I know that I'm extremely stupid for making so many obvious mistakes, but is there ANYTHING I can do?