Does it still show the balance or is it $0 (yet open status)? If it is at a $0 balance, I would leave it alone for as long as I could, as it will remain on the CR for up to 10 years after closing it. If it never closes, it will help you for a lonnnnnggg time.
If it is showing a balance--For the latter reason stated by TNWM, I would be a bit concerned about it. D/I ratio, too many accounts with balances, util...