Hello, notwise.
First, let me start by saying that I'm not too comfortable with using the word "convert" to describe my...er...conversion to atheism. "Convert" seems to have connotations of a emotional and spiritual bonding, as well as an acceptance of the dogma and ritual that attends the switch in belief. My acceptance that there is no god was entirely intellectual, based on my acceptance that there was no good evidence for the existence of a deity and that postulating a deity ended up explaining nothing. And accepting that there is no god does not entail the acceptance of any particular dogma or ritual, since there is no dogmas or rituals associated with atheism. But I don't want to quibble over semantics, we can continue to use the word "convert" if that is what you prefer, as long as we remember my concerns over the use of that word.
There is also some differences of opinion of the meaning of the word "atheism". When I use the word atheism, at least when describing myself, I take it to mean the belief that no god or supernatural deity exists.
Anyway, to describe my initial "conversion" to atheism, I will admit that it was a very shocking and depressing event in my life. Being steeped in the fundamentalist way of viewing things, I suddenly found my life without purpose, and I had trouble justifying taking a moral stance on things. Contrary to what some fundamentalists would say, I did not decide to not believe in god in order to justify my sinful life -- I really fought against accepting these beliefs because I found the implications of a godless universe disturbing and I tried very hard to maintain my belief in Christianity.
So my acceptance of atheism was really quite traumatic, and if I had my own free choice at that time I certainly would not have chosen it (although now, of course, I am glad that it happened). It took me a long time to learn how to develop my own purpose in life (or even what it means to have a purpose in life), and it took me a long time to realize that morals and ethics are not something that requires justification -- they are simply things that one feels.
As far as the process of my "conversion", that is pretty hard to describe, since I think a lot of the process was subconscious, and at any rate I am no better at figuring out why I think the way I do than I am at figuring anyone else out.
The first doubts came, I think, by actually reading the Gospels. I was a fundamentalist, of the religious right sort. But I could not square the Jesus' message in the Gospels with the right wing, conservative politics that the preachers were advocating from the pulpit. It didn't seem important at the time, but in hind sight I think this was the biggest source of my doubts. There were other aspects of evangelical Christianity that I found contradictory -- for example, what happens to, say, the souls of Pacific Islanders who lived after Jesus' sacrifice but before the arrival of the first missionaries -- I never found any of the answers I recieved to this question satisfactory. I recall that the differences in the accounts of the discovery of the empty tomb at the end of each gospel, not only a supposedly historical event but the most important historical event in the world, to be moderately troubling to the idea that the Bible was a literally accurate, divinely inspired work of actual history.
The final straw, though, was the theory of evolution. Once I decided to look into it (with the idea of refuting it), I found that Genesis simply could not be historically accurate. With that, my entire faith crumbled, and I eventually became an atheist.
I suppose one could ask why I didn't simply become a liberal, non-literal Christian along the lines of jar. I guess that is because I was so steeped in the fundamentalist faith that I couldn't disconnect any part of it from any other part -- the conservative politics, the literalness of the Bible, the existence of God -- if any of it was untrue, then none of it can be trusted. I also came to the opinion that there was no good evidence for the existence of a deity -- the only reason to believe was because the Bible said that one did. But if the Bible couldn't be trusted to be accurate in some things, then I saw no reason why its claim of the existence of god should be accurate.
That, then, is a description of my switch from Christianity to atheism. Is this what you were looking for?