Gneiss, i really recommend you read "the god delusion" by richard dawkins, "the end of faith" by sam harris, "god is not great" by christopher hitchens, and "the salmon of doubt" by douglas adams.
They cover the atheism thing very well and will answer your questions in much more detailed, entertaining, and informative ways than i could in a short post in a forum.
Also i recommend reading about russells teapot!
http://en.wikipedia.org/wiki/Celestial_teapot