Well, well. Paying off old credit cards/debts can hurt you if the statute of limitations has begun (9 yrs for most). I got bit a time or two from collectors trying to scam me into thinking that I had to pay...but found out after paying them a few hundred $ that I was just giving it away. Once I wrote to them about it, they replied telling me I was right, but wouldn't give what money they got back from me up until then.
It's really strange, but if you have a mess of old credit that is due, it's better off to pay the majority of them off. Your credit score will go down but you have to apply for new credit cards and use them wisely. Just make sure you have the money to pay them off, but just give them a hundred or two more than the minimum payment. Works really well. By juggling my cards in this manner my score in three months jumped to good and now I'm reaching Excellent.
You never really get out of debt if your smart. Keep them on your string.