RHEL 5.7 is only useful for:
Source: Red Hat Documentation (https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/5/html/installation_guide/) red hat enterprise linux 5.7 x64 iso 84
# Apply all pending updates yum update -y RHEL 5
At the time of its release, RHEL 5.7 was a bridge between generations. While the world was moving toward RHEL 6, many massive corporate infrastructures remained locked into the "Tikanga" (RHEL 5) ecosystem for its stability. red hat enterprise linux 5.7 x64 iso 84
This was the era where Red Hat introduced the modern way to register and update systems.