"If God created everything then who created God?" How does a Christian answer?

If you are a Christian like me who has tried to witness to someone, they may have asked you that question. How do you answer that question? In order to win them for Jesus, you have to try to explain to them in humanly understandable terms as many things as you can, right? Personally, I don't think "God has no creator he IS the creator" is going to cut it for most atheists. Fundies might say that I'm sucbing to science's trap of having to explain everything and I'm losing faith in God and turning to worldly methods. I don't think science is wrong or evil, it's just that the world has added many things that we, as Christians, cannot accept. God created science so that we could understand His creation, right? So if you know the answer and have convinced someone with your answer, please tell me. If you wish to answer this question, please do not verbally attack either side of the argument, Christian or atheist, just answer the question.