Should I pay off this old account?

It's always good to pay off your debts. When you pay off your debt, your credit utilization ratio drops. This helps to boost your score.

What state are you in? Have you checked the SOL period in your state? See if the SOL period is over, then you're free. Creditor can't get judgment against you now. As far as your credit report is concerned, the account will drop off in 2020. Only 2 years are left. Plus, the negative impact on your credit score gradually becomes low with time. So you can ignore this debt if you want.

You can forget about this debt Henry. there are only 2 years left. Have checked your SOL period? Which state are you from.
I would rather try to improve my credit score by properly handling my current debts and monthly payments, if I were you.