Completely off topic, well actually it's on the side topic, but all items purchased from a store are given an implied warranty of fitness for a particular purpose. The UCC guarantees that warranty. Pretty much means if you ask for something for a specific purpose, and the vendor says it will work, and it doesn't, you can get your money back. If you talk to someone high enough at the store, and point out the UCC implied warranty, good chance they'll give you your money back.
But sometimes no one has heard of it but there legal department (Warranty and UCC Warranty are a major topic in Contract Law at Law School and covered on the Bar Exam), so you have to take the store to small claims court. Pretty easy and cheap to file in small claims, and you're guaranteed in this case to get your money back and court fees as long as you can provide the information about what you asked it to be used for. Judge is pretty much guaranteed to side with you. http://en.wikipedia.org/wiki/Implied_warranty
is accurate, if bare bones on the topic.
Good Luck though :-D most major businesses will avoid litigation though, as they have better things to do with their time, so when the legal department hears about it, you get your money back.