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STATUS_BAD_MASTER_BOOT_RECORD
Do not diagnose MBR corruption from the symbolic name alone
STATUS_BAD_MASTER_BOOT_RECORD is a notable NTSTATUS catalog anomaly. In the current AllStat source and Microsoft’s common NTSTATUS specification, value 0xC00000A9 carries a message about an inappropriate token-object type, even though the symbolic constant name refers to a master boot record. Those two signals point at different subsystems.
Because of that mismatch, an automated diagnostic tool must preserve the numeric value, symbolic name, source table, and actual call site. FormatMessage resolves message text from message resources; the symbolic constant comes from headers. Neither is a substitute for stack/context evidence when the published pair is contradictory. Real MBR data has documented partition structures and can be queried through disk layout controls, but this status value alone is not proof that sector 0 or an MBR partition table is damaged.
Before running boot repair or rewriting partition data, identify the API that returned 0xC00000A9 and capture the native stack. If the failing path handles access tokens, investigate token object type and handle provenance. If the path truly performs disk-layout validation, independently inspect the drive layout and partition style. The contradiction itself is the reason to avoid name-based remediation.
What to inspect
- Preserve the raw value 0xC00000A9 and the native call stack.
- Do not launch MBR repair solely because of the constant name.
- Validate disk layout independently when the failing component actually processes partitions.
References
- Microsoft Open Specifications: NTSTATUS values
- Microsoft: Using NTSTATUS values
- Microsoft: FormatMessage
- Microsoft: PARTITION_INFORMATION_MBR
- Microsoft: IOCTL_DISK_GET_DRIVE_LAYOUT_EX
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