[CentOS] 4gb ram shows as 3.3gb

Hi,

Running Centos 5 (32bit)... running a server with 4gb of RAM and it's 
shows up as:

[root at ubercore1 ~]# free
             total       used       free     shared    buffers     cached
Mem:       3369544    2549668     819876          0      29008    2382360
-/+ buffers/cache:     138300    3231244
Swap:      6291448          0    6291448

I know 4gb is the limit for a 32bit OS but i thought it would be able to 
use all of it? Is there another kernel i was supposed to install?

--N