If someone got into your account and changed the password, you can try resetting it through email. Note that this will only work if they haven't already changed the email address on the account, and you will need access to the email account you signed up with.

If you've connected your account to Facebook or AIM, you can sign in using either, change the email address associated with the account, and reset your password to fix the issue.

If you cannot do any of these things, your account may not be recoverable. Read the following tutorial for more information that be potentially helpful:
- How to: Get Your Hacked Account Back