<prompt> Human: According to Credit Karma I have an Amex card with a 15,000 limit that was opened in April 2000, and has a 15 balance on it. The report says that Amex hasnt sent any data regarding this card since then.Im just starting to look into building my credit score, and as of right now I only have a single line of credit for 3,000 other than this Amex. My current financial goal is to buy a new car some time in the next couple of years, and while my score is pretty good low 700s I dont want to have to worry about being denied because I have 15k in credit tied up in a card I dont have. THere are also, of course, the concerns that theres someone out there who has my personal information and could be opening up cards in my name... but since the card is 14 years old and hasnt ever been used except maybe the one time Im not overly concerned on that front.What should I do, and what should I be worried about?  <response>: Could you be an authorized user on the card? Maybe from a parent? Credit Karma shows authorized user cards. 