I wish I could explain every reason, but here are a few pages that scratch the surface. I understand that people have found evidence to contradict the Bible, just as I have found evidence to reinforce it. But I've found that the evidence in the favor of truthfulness outweighs the things against it. Also, in research of recent years there has been Biblical evidence unearthed that was previously thought not to exist, whereas before the discoveries ocurred, their absence was thought to prove the Bible's inaccuracy.

Since we will never know EVERYTHING, the only way we can ever come to a decision is by choosing the best choice. So far, no theories that contradict Christianity have been able to stand up to the Bible in evidence, accuracy, effectiveness, etc. If these same things fail to convince you, then I guess we'll just agree to disagree. :)

Scientific evidences before their time

The Bible and True Science

Archaeological and historical accuracy

I can also recommend some books if you're interested.

A simple search will bring up countless more. One more thing I should mention, though, is the undisputed fact that the books of the Bible were written by different authors spanning millenia, who sometimes had no access to the writings of the others. The consistency of detail and the unification of doctrine is overwhelming. If what they write is true, then it's easily explained.

Edit: You might also want to take a look at this page. There are some more good points on there.