In a college class, if I have the right book, right edition, but different ISBN #, am I screwed?

I bought the textbook off of eBay and everything's right excpet for the ISBN #. Is this a huge problem?|||No. It's probably a special edition of the textbook. Also, the Instructor's copy has a different ISBN than the student's copy. If that's what you've got, I'd say that you're in great shape!|||Something else is wrong, because the ISBN # identifies the book, so if the number is wrong, so is the book or the edition. The only possibility I can think of is if your book is sold either separately, or as part of a package including software or something like that, the ISBN # could be different in each of those two cases. You may find that you are expected to have the software too, and in that case, if the software isn't sold separately, you might have to buy another book.