Minimum 133 MHz (Pentium-compatible); 550 MHz recommended. RAM: Minimum 128 MB; 256 MB-512 MB recommended.
This is what you will see when you boot from the ISO. server 2003 r2 iso
If you mount that ISO today, immediately disconnect the machine from the internet. Disable SMBv1, firewall everything except what is absolutely needed, and run it only in an isolated virtual machine. Minimum 133 MHz (Pentium-compatible); 550 MHz recommended