Ohhhhhh.... Thx Expeto. now I see why.
I installed fresh on a hardware with 4GB of RAM and it gave me el5PAE.
I do have a question now that I know what's up.
I got three systems total. One I just installed fresh with centos5 that gave me el5PAE. And two other systems which had installed OS but later upgraded RAM but only shows el5. How do I change this so it will boot with PAE mode? Any pointers?