If its an AOL account here is Apples help for that:
http://docs.info.apple.com/article.html?artnum=307459
Solution
AOL accounts are not able to be used on Apple TV. If you need to sign in to the iTunes Store with an AOL account on your Apple TV, your AOL account will need to be converted to an Apple ID. iTunes Store Support can do this conversion for you. To reach them, follow these steps:
Go to the iTunes Store Support page and fill out the form at the bottom of the page. If you see a "Contact Us" button instead of a form, click it and then follow these steps:
In the Category section, choose Account or Billing.
In the Sub-Category section, choose I can't sign-in with my AOL account.
Ignore the Info field that appears on the right, and explain your situation in the "Ask Your Question Here" field at the bottom.
Click the Send button to send your request to iTunes Store Support.