I think I understood you wrongly, Dione, and perhaps that got the discussion going in the wrong direction.
I think there are several ways of approaching this question, because in fact the word believe is used in several different ways. Colloquially, it's quite often used as a synonym for 'I think' -- as in, 'He should be here in five minutes, I believe he was getting the 10.30 train.' And by the same token it is often used as a synonym for "I am of the opinion that", as in "it's my belief that if Gordon Brown had called an election in the autumn of 2009, he would have won it".
Neither of these very common usages have much relation to the definitions cited by Pedro and Technodad, in which 'believe' carries a lot of epistemological weight -- and their definitions are phrased to make any belief inherently fallacious because, by definition, a belief lacks evidence.
However, specialsubject's example is an interesting one: "I believe that if I drop this laptop, it won't hit the ceiling", because this, for specialsubject is an example of a belief where there is evidence. Except that there isn't as Hume showed as long ago as the eighteenth century, we cannot take past occurrences as evidence of future recurrences of the same phenomena. Just because the laptop hit the floor there is no certainty that it will not float up to the ceiling next time, because there may be larger patterns at work of which we are unaware. Nevertheless, we normally assume that past experiences do predict future phenomena, and this is, in Pedro and Technodad's sense, a "belief": an acceptance that something is true without verifiable evidence. In that sense we all have beliefs about the world around us even those people who think they do not have any beliefs.
Just to clarify two points from my post. The first is that the Indiana Jones invisible bridge was an analogy not of my own supernatural powers (which I don't have), but of the way that belief in God means I trust what I cannot see. I do walk over the bridge (just as I eat and drink and pay bills) in the sense that I depend upon God.
And the quote from Lewis, I understand not as meaning that Christianity is a prism, but that it is the medium through which Lewis sees everything. Another way of putting it is the wonderful line from Psalm 36: In you is the fountain of life; by your light we see light.' God is prior to and outside of the cosmos, and only by his light (or through his existence) can we know anything of the cosmos. But that's a bit of a tangent to this discussion.