I disagree with a lot of the people that immediately jump on others for resurrecting old threads. If you're adding something significant to the conversation, then it's a good choice. If you've read the entire thread but still have questions about that topic that aren't covered, then it's a good choice *and* avoids the "did you use the search?" posts, because you obviously did.
New posters often get caught responding to old threads because they don't realize they're old. These cases can be politely corrected, but there's no need for a dozen people to all say "this is useless", once is enough.