Ah, the smell of old history books!
List all course prerequisites (if any), and list when you completed them:
I do not have the necessary prerequisites and am requesting that the prerequisites be waived.
I do not currently have the prerequisites but will have them transferred from another institution before the semester begins.
I do have the prerequisites, but for some reason, the computer is blocking my registration.
There must be a compelling reason why you should not delay taking the course until a subsequent semester. An example of such a reason is that you have completed all other requirements for graduation.
Specify the reason in concrete detail:
Note: This does not suffice to say that the course is a prerequisite for another course, unless, there is also a clear and cogent explanation of why you cannot meet this requirement in a later semester.