Creating Pivot Table

Hallo,

I have a table with 3 columns:
table tbl_user_class
===============
user_id (int) PK
class_id (varchar(20)) PK
class_value(varchar(100))

values are like so:

user_id class_id class_value
======================
1 firstname Rogier
1 lastname Doekes
2 firstname Mary
3 lastname Smith
.....

I would like to create result set in the following format

user_id firstname lastname
====================
1 Rogier Doekes
2 Mary Smith
......


How do I accomplish this? I tried using CASE WHEN statements but the best I could come up with was this:
1 Rogier null
1 null Doekes
2 Mary null
2 null Smith

when I did the following t-SQL statement:
select userID,
CASE WHEN classID = 'firstname' THEN classvalue END as 'firstname',
CASE WHEN classID = 'lastname' THEN classvalue END as 'lastname'
FROM tbl_user_class

Thanks for any help,

-Rogier Doekes