Backup Exec 15 requires a valid license key. The ISO itself is the installation media. You cannot legally download or use it without an active entitlement or a purchased license from the past.
Occasionally, legacy trial ISOs are mirrored on tech community forums, but be cautious—always verify the MD5 or SHA-1 hash of the file to ensure it hasn't been tampered with. Symantec Backup Exec 15 Download Iso
If you're unable to find the ISO file on the Broadcom Support website or prefer a more direct approach: Backup Exec 15 requires a valid license key
Before you spend time downloading the 4 GB ISO, ensure your hardware and software meet these minimums for Backup Exec 15: Symantec Backup Exec 15 Download Iso