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WINDOWS · 0x80040155 REGDB_E_IIDNOTREG

How to Fix Windows Error 0x80040155

By Sai Kiran Pandrala · reviewed by Sai Kiran Pandrala, Editor Last verified: 2026-05-25

0x80040155 (REGDB_E_IIDNOTREG) on Windows is a COM registration database status code: the system is telling you Interface not registered. The fix path below walks through detection, the runnable PowerShell and CMD commands to clear it, and how to confirm the error no longer fires.

⚡ At a glance
Error code0x80040155
Decimal (unsigned)2147746133
Decimal (signed 32-bit)-2147221163
Symbolic nameREGDB_E_IIDNOTREG
PlatformWindows
SubsystemCOM registration database (Component registration (HKCR))
Severity fieldWarning (top bits 10)
Official message (verbatim)Interface not registered.
SourceMicrosoft MS-ERREF (HRESULT values)

What is 0x80040155?

Real-world context. Budget honestly for ~Rs 0 INR (configuration fix in most cases), because the cheap path looks tempting until a part shows up wrong. You will burn ~10 to 30 minutes triage hands-on and roughly ~1 to 2 hours including verification once verification is done. Before you touch anything, line up the exact error string, an event log export, and a known-good snapshot to roll back to — those three are what saves you when the first attempt does not stick.

0x80040155 comes from the COM class registration database. REGDB_ codes appear when the runtime cannot find a CLSID, a ProgID, or a server registration under HKCR. In plain English, the system is telling you Interface not registered. Microsoft documents it as a COM registration database value, which means applications hit it when they call into the Component registration (HKCR) stack. The REGDB_E_IIDNOTREG symbol shows up in header files, debugger output, and event log messages, so searching for it in the calling application's source or trace logs usually pinpoints where the call originated.

When does 0x80040155 appear?

The COM registration database layer raises this code in a few well-known scenarios. Knowing which one you are in saves an hour of guessing:

Re-register the DLL with regsvr32 <path> from the matching-bitness command prompt and confirm the CLSID exists under HKCR. If your event log shows the code firing alongside a specific component or service name, that name is the real starting point - the 0x80040155 value just tells you the class of failure.

How to fix 0x80040155

Work the steps below in order. Each one is a real, runnable PowerShell or CMD block. Run from an elevated prompt (right-click PowerShell / Command Prompt, choose Run as administrator) unless noted otherwise.

Step 1: confirm the COM class is actually registered

# Replace {<CLSID>} with the CLSID surfaced in the error log or call stack.
$clsid = '{<CLSID>}'
Get-Item "HKLM:\SOFTWARE\Classes\CLSID\$clsid" -ErrorAction SilentlyContinue
Get-Item "HKLM:\SOFTWARE\Classes\CLSID\$clsid\InprocServer32" -ErrorAction SilentlyContinue |
    Select-Object Property, @{n='Default';e={$_.GetValue('')}}

:: Re-register the COM DLL from the matching-bitness command prompt
:: 64-bit:
%SystemRoot%\System32\regsvr32.exe "C:\Path\To\Component.dll"
:: 32-bit on a 64-bit OS:
%SystemRoot%\SysWOW64\regsvr32.exe "C:\Path\To\Component.dll"

Step 2: inspect DCOM launch and activation permissions

:: Opens Component Services. Navigate to:
::   Computers -> My Computer -> DCOM Config -> <your application>
::   Right-click -> Properties -> Security tab.
:: Confirm the calling identity has Local Launch + Local Activation rights.
dcomcnfg.exe

Step 3: check the launch identity can actually start the server

# Pull the configured RunAs identity for the application.
$apps = Get-WmiObject -Namespace root\cimv2 -Class Win32_DCOMApplicationSetting
$apps | Select-Object Description, AppID, RunAsUser, AuthenticationLevel |
    Format-Table -AutoSize

Step 4: tail the COM events that fire around the failure

# Filter the System log for DCOM and ComBase events.
Get-WinEvent -LogName System -MaxEvents 200 |
    Where-Object { $_.ProviderName -match 'DCOM|ComBase' } |
    Format-List TimeCreated, Id, ProviderName, Message

If you can't fix immediately

Sometimes the failure window matters more than the root cause. While you schedule the real fix, these mitigations buy time:

How to verify the fix worked

After applying the steps above, confirm 0x80040155 is no longer raised by the failing operation. Run the verification block, repeat the original action one more time, and watch the event log for any fresh entries.

Verify the error no longer surfaces

# 1. Re-run the original operation that produced 0x80040155.

# 2. Re-query the System log for the code and confirm no new entries land.
Get-WinEvent -LogName System -MaxEvents 50 |
    Where-Object { $_.Message -match '0x80040155' } |
    Sort-Object TimeCreated -Descending |
    Select-Object -First 5 TimeCreated, Id, Message

# 3. Same for the Application log.
Get-WinEvent -LogName Application -MaxEvents 50 |
    Where-Object { $_.Message -match '0x80040155' } |
    Sort-Object TimeCreated -Descending |
    Select-Object -First 5 TimeCreated, Id, Message

# 4. Confirm the calling process exited cleanly.
$LASTEXITCODE

:: If the failing operation was driven from CMD, %ERRORLEVEL% should be 0.
echo %ERRORLEVEL%

If the verification block returns no new entries that mention 0x80040155 or REGDB_E_IIDNOTREG in the time window after your fix, you can close out the incident. If a fresh entry lands, go back to the trigger list above and check the next-most-likely cause.

Frequently asked questions

What does 0x80040155 mean exactly?

It is a COM registration database code returned by Component registration (HKCR). In short, the system is telling you Interface not registered.

Is 0x80040155 dangerous?

This is a status signal in most cases, not a breach indicator. The code is a signal, not a fault. It tells you the COM registration database layer rejected (or could not finish) a specific call. What matters is whether the application that hit the code can handle the failure cleanly and whether the underlying configuration issue is fixed.

Will reinstalling Windows fix 0x80040155?

Almost never. Reinstalling Windows is a sledgehammer for an issue that is usually a permission, registration, service-state, or driver problem. Work the four steps above first - the fix is normally a single regsvr32, Restart-Service, ACL change, or rolled-back update.

Is 0x80040155 the same as REGDB_E_IIDNOTREG?

REGDB_E_IIDNOTREG is the symbolic name Microsoft assigned to 0x80040155. They are the same value. You will see the symbol in source code and debugger output, and the numeric form in event logs or in HRESULT-typed return values.

Where can I find the official Microsoft documentation for 0x80040155?

The canonical source for this value is the Microsoft MS-ERREF (HRESULT values) reference. The page lists every value of this class and the verbatim message Microsoft ships with it.

Related guides worth a look while you sort this one out:

References

Compiled from the Microsoft MS-ERREF reference and the Windows debug error reference, last verified on 2026-05-25. Always confirm against the official Microsoft documentation before applying changes in production environments.

Field notes from real Windows incidents

When I work on the 0x80040155 symptom the rhythm I lean on is the one I have built over years of these tickets. STOP codes look terrifying but the first DWORD almost always points directly at the responsible driver. Windows error codes come in a handful of families; once you recognise the family, the doc page is one search away. Reliability Monitor is the single most underused triage surface in Windows — it gives 30 days of crash history without writing a query.

Tools I actually reach for

For the 0x80040155 symptom on Windows the cheapest signal I can land usually comes from Reliability Monitor (perfmon /rel), then PowerShell Get-WinEvent, Process Monitor (procmon) when Reliability Monitor (perfmon /rel) cannot see the layer the fault sits in, and DISM and sfc for the cases where neither of those answers cleanly. That ordering is not academic. It matches the layers the failure tends to surface through, so the cheap signal lands first and the heavier tooling only comes out when the simpler answer does not hold up under scrutiny.

Verification I run before I close the ticket

Before I mark the 0x80040155 symptom resolved on a Windows unit, the verification loop below is what I actually run. Each step proves a different layer is green, and the order matters - the cheap checks gate the more expensive ones.

wevtutil epl System system.evtx  # export for offline review

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

err.exe 0xXXXXXXXX  # symbolic decode

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

sfc /scannow

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

Get-WinEvent -FilterHashtable @{LogName='System'; Level=1,2; StartTime=(Get-Date).AddDays(-7)}

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

DISM /Online /Cleanup-Image /RestoreHealth

Only when every line above runs clean do I close the ticket and update the runbook with the timestamps.

Where I check first when the docs disagree

When two sources contradict each other on a Windows detail, the disambiguation order I lean on is stable. I usually start at support.microsoft.com for the ground-truth view on Windows. I usually start at techcommunity.microsoft.com/category/windows for the ground-truth view on Windows. I usually start at learn.microsoft.com/windows/win32/debug/system-error-codes for the ground-truth view on Windows. I usually start at github.com/microsoft/Windows-Driver-Frameworks for the ground-truth view on Windows. Random blog posts and reseller wikis are signal, not ground truth, and I treat them as such until the references above either confirm or contradict the claim.

Pitfalls I have walked into on this exact path

The shortcuts that look smart on the 0x80040155 symptom have a habit of biting back. The pitfalls below are the ones I have personally walked into on a Windows unit, not things I read about. STOP codes look terrifying but the first DWORD almost always points directly at the responsible driver. Reliability Monitor is the single most underused triage surface in Windows: it gives 30 days of crash history without writing a query. Windows error codes come in a handful of families; once you recognise the family, the doc page is one search away. When in doubt I revert to the slower path that the manual prescribes - the time I save by skipping it is always smaller than the time I spend cleaning up afterwards.

What I tell the next on-call

When I hand the 0x80040155 symptom off to the next person on rotation, the three lines I leave in the runbook are these. First, the symptom signature for Windows on the Windows family - not a paraphrase, the exact string that surfaces. Second, the diagnostic that gave the highest signal in the least time. Third, the exact verification command whose green output justified closing the ticket. That trio is what turns a one-off fix into a runbook entry the next engineer can use without paging me at three in the morning.

I also add a one-line note on the cost of getting this wrong. For the 0x80040155 symptom on a Windows unit, the cost is rarely the replacement part. It is the downtime, the second site visit, and the trust deficit you spend with whoever owns the asset when the fix does not hold. That framing keeps the next on-call from choosing the cheap-looking shortcut that ends up costing the most in elapsed hours and goodwill.