PAE stands for Physician Address Extension and is an option for the Linux kernel which will allow you to access 4gig of RAM on a 32 bit kernel setup.

install as root:

yum install kernal-PAE

Reboot the computer and a new kernel option, indicated by the suffix PAE, is available. Boot that kernel. In the terminal type:

free -m

and you should see a print out with a number close to 4025 listed under total.

as root remove the default kernel:

yum remove kernel