The "72 Virgins" story is NOT PART OF THE KORAN. Instead, it is in an Hadith, and these items are simply stories about the life and times of the Prophet. Many of them were made up for political purposes, or inheritance (the prize being the Islamic state ~ see Shia).
No Christian should place great faith in the reliability of any Hadith! Few reflective Moslems do. Most folks, though, keep their mouths shut because there are these ignoramuses out there who will kill you for criticizing the Koran or the Hadiths.
The "72 Virgins" story is one of the more questionable items in the collection.
I've more than "hadith" with these terrorists using their weird beliefs to justify heinous crimes...