I think my son has been viewing inapproprite sites on the internet. He has deleted the history. Is there an easy way to undelete or vew the history? I have heard about index.dat but have heard they are near impossible to read. Is there an easier way?

Sorry to say, but once it's deleted it's gone for good.
There are some applications that claim to be able to undelete, but I have yet to find one that actually works for internet history.

You could always download a free filter, just make sure that you choose a password that he won't be able to guess

Try browsing through the cookies. He may not have deleted those and they can give you a clue. The filter is a great suggestion to block offending sites . If you're more interested in catching than in preventing I think you can find software that will log web usage quietly in the background (sort of keeps it's own history)

Keep the computer in an open area. Be around when he's on the computer.