No, that's not an accurate estimate. The actual number was probably less than a million and maybe even less than that. But the 5 million is what many New Age and Wiccans and feiminists like to spout off with to prove their point. http://www.draeconin.com/database/witchhunt.htm is an excellent, factual, well-researched article into the subject.

Also http://www.religioustolerance.org/wic_burn2.htm That particular website is one of my favorites for real information on this kind of thing.

http://dir.salon.com/story/books/review/2005/02/01/witch_craze/index.html is an article directly referencing the DaVinci Code.