"78081g503.ic655 not found" is a specific technical message generated by
Search for the File:
Ensure your ROM/BIOS set matches your MAME version. If you are using MAME 0.275, you need the 0.275 ROM set. Placement: Keep the BIOS file zipped ( coh1000w.zip ) and place it directly in your directory. Common Issues and Questions (FAQ) - MAME Documentation 78081g503.ic655 not found
Antivirus False Positives: Because .ic655 files are non-standard, some aggressive antivirus programs may flag them as "unknown threats" and quarantine or delete them. "78081g503
How to investigate — systematic steps