Look for files named like: redhat-5.3-i386-disc1.iso , redhat-5.3-i386-disc2.iso . Typical size: ~650MB per CD (actual size is ~600MB because 1999 CDs were smaller).
It was the first to offer full support for Intel’s Core i7 (Nehalem) processors, including features like Extended Page Tables for enhanced virtual machine performance. Red Hat Linux 5.3 Iso