I think you mean "warranty," which is a type of guarantee given when you buy something. If something goes wrong with the product you bought, you are either guaranteed a replacement of the product or your money back under the terms of the warranty. A "warrant," however, usually refers to a search warrant or an arrest warrant, which is issued by the justice system when somebody has commited a crime. The warrant gives law enforcement/police the legal right to search somebody's property or bring them to jail. "To warrant" is also used as a verb to mean "to justify"... i.e. "I know he was upset that she spilled coffee on his shoes, but I don't think that warranted his breaking all her windows." So nope, they are not the same thing!

guarantee................a promise for doing something. warrant....................a paper of garantee.