Since Windows 2000 a login with a user name (or profile as it is sometimes called) is mandatory. In older Windows versions you could decide if you want to login using a profile or not. Still you had to enter a name that the system would use.

The easiest way to find out your user name is to start CookieCooker and select "Register" via the web interface.
The following window will appear. In this example the Windows user name is "oli".

Please copy that name exactly to the registration form. Otherwise your registration number will not work. If no name is shown in CookieCooker's window then please enter nothing in the registration form. (This happens with a few old Windows versions.)