Before diving into theory, here is the fastest way to bypass the error.
The "FATAL ERROR: no CD-ROM found" error occurs when the MikroTik RouterOS installer boots but cannot find the installation media (CD or USB) to continue the process . This typically happens due to UEFI/Legacy BIOS conflicts fatal error no cd rom found mikrotik
To truly fix this error, you must understand the legacy boot process. Before diving into theory, here is the fastest