The wider belt is the alternator and the narrower is the AC. If it is the alternator belt, you need to replace that or the battery will eventually run out. I also think from your description that it is the alternator belt, since you need to remove the alternator belt to get the AC belt off. If it happens to be the AC belt, you can just ignore.
Last edited by yiranhu; 01-30-2009 at 12:08 AM.