There are two codes. The one you get for pre-ordering is the 18 digit code. This one is registered at http://preorder.na.finalfantasyxiv.com/
Once you register that one, you get another code that you enter in the launcher.
Try logging in through the website I linked above. You said...
When I login in at http://preorder.na.finalfantasyxiv.com/ it sends me to a new window displaying my email address and wanting information to complete a new account
This is right. There is a Square Enix ID which you use to link your FFXI or FFXIV service accounts to, but there is also a Square Enix Members account. It's different, but you can link your Square Enix ID to this account. Go ahead and complete the registration for this website. Once you finish setting that up, you'll probably get redirected back to the pre-order website but if not then go to http://preorder.na.finalfantasyxiv.com/ again.
From there, click your name at the top right of the screen and select 'My Profile'. Next, click the button with the gear at the top right that says 'Settings'. Add your name, date of birth and anything else it asks for. Make sure that you select 'English(US)' here as your language. Save everything and go back to http://preorder.na.finalfantasyxiv.com/
Maybe there was a step in there that was missing. Let me know what you come up with.