I'm not sure what "RHELS 5" is (Red Hat Enterprise Linux? RHEL?), however have you attempted to do the following?
1) How did you install "RHELS 5"?
Was it while the laptop was connected to a aexternal monitor, or when it was stand-alone?
2) Have you checked the dual-head configuration for X?
At the command prompt, type "system-config-display", then go for the "dual-head" display tab.