I come from Christianity.SE, where I asked almost the same question. Isaac Moses assured me that the question would not be disrespectful and could be asked here.
God's name is written as the Tetragrammaton יהוה (YHWH) in the Torah. The name is not vocalized in the manuscripts and I know it's considered ineffable by Jews and thus not said aloud. For that reason, the original pronunciation hasn't been preserved (as far as I know).
Christians commonly suggest the pronunciations Yahweh and Jehovah (which should of course be pronounced like "Yehovah"). Long ago I heard it claimed that the vocalization Jehovah is based on a misunderstanding, but I don't remember the reasoning.
What is the probable original vocalization?