If that doesn't help, you will need to create a ticket. Please include as much information as you can including your username, birth date, and the email address you used when you signed up. You can also include any information about your Neopets and items that you think will help identify you as the owner.
I tried to have my password sent to me, but it didn't work. Now what do I do?
First, check your spam email folder to make sure that the email containing your password wasn't accidentally labelled as spam.