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REGDB_E_CLASSNOTREG
Class not registered
When Windows returns REGDB_E_CLASSNOTREG—HRESULT 2147746132, 0x80040154, signed -2147221164—The documented description is “Class not registered”. The actionable meaning is the requested CLSID has no usable COM class registration in the caller’s context. The surrounding operation is CoCreateInstance, CoGetClassObject, moniker binding, or another class activation request.
Precise failure point
COM registration is architecture-, scope-, and identity-sensitive. A key visible in Registry Editor is not proof that the failing process sees the same view or that the values form a coherent activation contract.
- Associate this result with one exact operation in CLSID/IID registry lookup, InprocServer32 or LocalServer32 metadata, interface proxy registration, package policy, and threading-model interpretation.
- Confirm that this result came from CoCreateInstance, CoGetClassObject, moniker binding, or another class activation request, rather than from cleanup or a wrapper that ran afterward.
Diagnostic evidence
- Log CLSID, class context, architecture, package identity, and user SID.
- Inspect the effective registration rather than searching for similarly named DLLs.
- Confirm that the registered server exists, matches the machine architecture, and exports or registers the class.
Resolution path
- Identify the exact object, method, and lifecycle phase involved in CoCreateInstance, CoGetClassObject, moniker binding, or another class activation request.
Distinct causes
- It can result when the component is not installed or registration was removed.
- It can result when 32-bit and 64-bit processes see different class registrations.
- It can result when the CLSID is correct for another product version, package, user, or deployment scope.
Retry policy
Correction. install or repair the owning component, or use the CLSID documented for the deployed version. Retry condition. Retry only after registration or deployment changes; copying a DLL without its installer is not a valid fix. Before repeating the operation, complete or roll back the installer transaction, re-read the exact user or machine registry view, and discard class factories obtained from superseded registration.
Practical scenario
A desktop tool is rebuilt as x64 while its legacy in-process plugin remains x86; selecting an out-of-process bridge or installing an x64 plugin resolves activation.
Difference from related HRESULTs
CLASS_E_CLASSNOTAVAILABLE means a class factory was found but could not supply the class; it means activation could not locate usable class registration.
Developer and administrator guidance
References
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