Du kannst ja mal versuchen die "ATX"-Funktion zu disablen indem du im BIOS die Power-Einstellungen veränderst. So inetwa in dieser Art:
Suspend Mode [Disabled]
Repost Video on S3 Resume [No]
ACPI 2.0 Support [No]
ACPI APIC support [Disabled]
APM Configuration:
Restore on AC Power Loss [Power Off]
Power On By RTC Alarm [Disabled]
Power On By External Modems [Disabled]
Power On By PCI Devices [Disabled]
Power On PS/2 Keyboard [Disabled]
Power On PS/2 Mouse [Disabled]
Mal sehen, was dann beim Ausschalten passiert
Gruss Wildfoot