RHEL 5 Rescue vs RHEL 6 rescue in VMware - Disk Not Found

i have a rhel 5 VM im trying to rescue. After booting the RHEL 5 rescue iso, it fails to find the boot disk. But it works fine when booting the RHEL 6 rescue iso. The underlying boot disk is RHEL 5...

any thoughts? Why be visibile on the RHEL 6 rescue iso but not RHEL 5?