I originally started out this post with the idea of making a simple movie on how to track changes and delete those changes in Word. Realizing that I have Word 2000 and many others have moved on to Word 2003 and Word 2007, I decided to begin with some research to see what the differences were. In that research I found a great site to help with Word, so I'll point you there instead, Shauna Kelly's Making the Most of WORD in Your Business.
If you are still reading, you might have been asking yourself, "Why making a movie on something trivial like this?" Well, Shauna has captured some specific examples for that too. In fact, she's listed 10 real examples where not minding those tracked changes has led to embarrassment (or more).
Finally, if you just want to know more about tracking changes and versions in Word, here's the link to the article on Shauna's site.