I am trying to execute following sql script in sql-server 2000 query analyzer

CREATE TABLE user_courses (user_id varchar(30) NOT NULL PRIMARY KEY,
course_id varchar(10) NOT NULL PRIMARY KEY)

Its give's me following error :-
Cannot specify multiple primary key constraint

Hence I am not able to ceate table with multiple primary keys. So can any one tell me how to get this done?.

Secondly, Primary key must be unique i.e duplicate values are not allowed in P.K field. But in this case since I am declaring two fileds as primary keys.
Will it allow me to have following records in the user_courses table?
user_id(P.K) course_id(P.K)
bob CRS235
alice CRS235
Tim CRS235
tom CRS635

So, if we consider both the fields as primary keys together than I am not voilating Uniqueness constraint. But, if I look at course_id alone then I am voilating uniqeness property?