1.) Head to a GameStop of your choice & Buy a Wrath of the Lich King Box.
2.) Open the Box, Take a picture of the CD-Key, or use it right then if you wish.
3.) Make small scratches on the CD, then Box it back up and take it to the Retailer you bought it from to return it & claim it doesn't work.
4.) They will give you a new Wrath box, and take your old one.
5.) Re-peat the same steps above, make sure you have your receipt, and take it to a Game Stop and explain the situation to them that they are closer to you than the other, and you'd like to return this because the CD doesn't work.
6.) They'll take the return, and give you a new box.
7. Sell the 2 CD-Key's that are unused for Profit.
It has worked for me several times, if you space it out right and scope the store for when there are different workers there, it can work more than once at the same store.
I've been doing this for awhile now, and just use the Profit you gained from selling the unused cd-key's to head to different retailers such as a Mall outlet store, and do the same thing, just make sure there are at least 2 of the same stores locally in town.
Effectively, this could work for any PC Game, but I only do it for World of Warcraft copies. I've made several hundred dollars doing this.