I'm assuming that the question you are asking is:

Is the ID column duplicated because it is in the clustered and non-clustered indexes?

The answer is interesting, and the full detail depends on whether the index is declared as UNIQUE or not.

Rather than give the answer directly, I'm going to ask you to read this blog entry by Kalen Delaney.

Try the code out, and see if you can answer your own question - it's the best example I have seen to illustrate the finer points of index structure - particularly as it applies to your question.

Post back if you have further questions after reading the blog.

Paul