DISC I/O ERROR ID = 0000
Normally happens right before a loading screen. This error is thrown when a file requested for loading isn't found in the CD table of contents (should never happen on an original CD, except if the TOC zone is physically damaged).
If the CD is an original one, it's certainly dirty or scratched.
If the CD is a copy, it's certainly re-authored (not an exact copy of an original). Even if the files are the same, the CD image structure can be altered and detected.
This is the case for games using file versions in their ISO 9660 structure, like Metal Slug 2. Most Windows ISO image editors strip the versioning info which is needed by the game to identify the files. Use mkisofs or edit the loading tables in the main PRG file.
- "WARNING BANK ERROR": Cartridge_self-checking. Cartridge dirty, bad 74LS74 for bankswitching.
- "WARNING COPYRIGHT MESSAGE": Slot_check_security. Clear backup RAM. Bad uPD4990. Bad BIOS ROM.
- "Z80 ERROR": Z80 ERROR
See BIOS Self-tests.