Evolution of Genetic Material??

I want someone who believes in evolution to explain to me how a DNA double helix is supposed to have evolved. I have heard some people say that DNA evolved from RNA but that begs the questions, how and why? The only organisms that have RNA and not DNA are retroviruses, which need the DNA of another organism to reproduce, so they couldn't have been living long enough for the necessary mutations to evolve. Also, how does this material evolve to become double-stranded instead of single-stranded? Why the switch to DNA, since it can be argued that RNA would be a better template? It seems to me that DNA screams intelligent design.

The problem with something in Discover Magazine is that is still a designed experiment. Leaving something to sit in a test tube and never doing anything to it will never lead to life. Yes, I am aware of the experiment that is supposed to have replicated 'initial conditions' on Earth that got some amino acids to form, but it only got about 8 out of 22. Not a very good ratio for an experiment that was still designed. I think the key word in one of the posts is 'imagine.' Where does this magical self-replicating RNA molecule come from? And if DNA is more stable, why do we still have RNA, and why can't DNA do everything RNA can if DNA is more evolved? RNA can serve more functions. The simple fact is that DNA is useless without RNA--because DNA is not self replicating because it has no enzyme activity, and RNA cannot replicate itself without DNA either. Both must have come into existence at the same time. Therefore, it must have been created. What is the simplest organism you can think of? Probably some kind of virus, which still has how many genes? The smallest one I have ever heard of still has a few hundred genes. The 'simplest' organism on Earth is still far to complicated to ever have evolved step-wise.