Q: wrong apple id registration, what can i do to change it?

http://iforgot.apple.com/ or http://register.apple.com/

You may also want to contact AppleCare directly:

http://www.apple.com/contact/phone_contacts.html

AppleCare is not available for any Classic products, for which this forum you posted to refers to.  Classic is 13 years old.  User to user inquiries regarding your Mac, should be posted to the forums listed on this tip in their correct forum:

Site map of Communities and Categories