How this can be done: When a visitor click checkout using anonymous checkout (checokut without account) and when hi finish his order on the checkout confirmation page to ask him if he want to have an account in the web site to fill only the password fields, as other fileds are already filled in the checkout without account form.
Is there anybody did it already ? 
Isn't that part of the standard cart if you have a setting checked (something like “allow user to create profile after checkout”.
Yes, Thanks
Yep I think thats what I seen in demo