BSOD 76 (FATAL_UNHANDLED_HARD_ERROR): causes and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: Windows received an unhandled hard error severe enough to stop the system.

Could be also:
Constant	Type	OS
ENOTUNIQ	errno	Linux
EPROCUNAVAIL	errno	Mac

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FATAL_UNHANDLED_HARD_ERROR

Fatal hard-error escalation for FATAL_UNHANDLED_HARD_ERROR

FATAL_UNHANDLED_HARD_ERROR is bug check code 0x0000004C. Hard errors are kernel-mediated serious error notifications. This bug check means the hard-error path reached a fatal condition, often because a critical subsystem, device, or image failed in a way the OS could not continue past.

How to read it in a dump

Inspect the hard-error status code and the process or subsystem that raised it.
This is a wrapper around a fatal status; the nested status and stack provide the real cause.
Do not stop at the symbolic name without decoding the embedded NTSTATUS if present.

What to check

Run !analyze -v and inspect the arguments for a nested status code.
Check storage, image load, system file, and critical subsystem errors near the crash.
Preserve event logs and dump data because the hard-error origin may be earlier than the final stop.

References

Dump evidence

Preserve the complete dump, the four bug-check parameters, the exact Windows build, loaded-module list, and the event timeline immediately before the stop. AllStat summarizes the condition as “this result”; that sentence identifies the failure class, while the parameters and stack determine which object, driver, processor, or subsystem instance was involved.

Analysis order

Run WinDbg !analyze -v, then inspect the documented meaning of each parameter instead of relying only on the probably-caused-by line.
find the earliest abnormal event: driver update, firmware change, device reset, storage error, verifier report, resource exhaustion, or application hang connected with fatal / unhandled / hard.
keep third-party filter, security, storage, graphics, and virtualization drivers in the module inventory; removing evidence before dump analysis can obscure the responsible path.

Do not repeatedly reboot a machine affected by this result before collecting the dump and event logs. Recovery actions should follow the component identified by the stack and parameters, not merely the symbolic stop-code name.

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