Modern antivirus software is aggressive. The DRM-free or cracked versions of older games often trigger false positives. Sometimes, the heuristic analysis of an antivirus program will flag the massive .dat file as suspicious "packed" data and quarantine or delete it without notifying the user.
Both files must be present, matching, and uncorrupted. Missing either file, or having version mismatches (e.g., an old .fat with a new .dat ), will cause audio to fail partially or completely. Modern antivirus software is aggressive