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Runtime Error 339 means that an application cannot load a required ActiveX control, usually an .ocx file. The filename in the dialog—such as COMDLG32.OCX or MSCOMCTL.OCX—is the key to a safe fix. Obtain that exact component from Microsoft or the application’s vendor, register it from an elevated Command Prompt with the correct 32-bit tool for a legacy 32-bit control, and then repair or reinstall the application if the error remains.
What Runtime Error 339 means
The error is a component-loading failure, not a single universal “missing file” problem. Windows displays the number 339 when an application asks for an ActiveX control and cannot load it. The dialog normally identifies the control, for example:
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COMDLG32.OCXMSCOMCTL.OCX- Another application-specific
.ocxfile
Read the filename exactly, including its spelling and extension. Two different programs can show Runtime Error 339 while requiring different controls. Installing or registering a similarly named file will not solve the problem and can introduce a version mismatch.
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1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsThe wording “or one of its dependencies” is important. An OCX can be present and registered while a second library that it needs is missing, incompatible, or built for a different architecture. For that reason, a successful registration message is evidence that Windows accepted the registration command; it is not proof that the application has the correct version or a complete dependency chain.
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Capture the exact details before changing anything
- Copy the complete error text. Record the control filename exactly as shown. Do not rely on memory or a search result that mentions a different OCX.
- Note the application that fails. The application’s installer may be the authoritative source for the control, especially if the program uses a private or older build.
- Record whether Windows is 32-bit or 64-bit. Many controls used by Visual Basic 6 applications are 32-bit legacy components. On 64-bit Windows, the registration utility must match the control and the application.
- Do not delete an existing OCX yet. Replacing a file before identifying its source and version can make the original application harder to repair.
Choose a trustworthy component source
Microsoft Visual Basic 6.0 Common Controls update
For applications that specifically require the Visual Basic 6.0 common controls, Microsoft provides an official Common Controls package containing mscomctl.ocx and comctl32.ocx. Use the Microsoft package when the filename and the application’s documentation match those controls. An official installer is preferable to downloading an isolated file from an unfamiliar OCX site because it supplies the files as a known package rather than as an unverifiable copy.
The application’s own installer
If the failing program has a repair option or a current installer, use that route when possible. The vendor’s installer can place the expected OCX version alongside the application and install related dependencies together. This is particularly important when the error returns after registration or when the application was copied from another computer instead of installed normally.
Sources to avoid
Do not substitute a random OCX download, a file with a similar name, or a “registry fix” that promises to register every missing component. Such files may be the wrong version, may target a different architecture, or may omit dependencies. A registry cleaner cannot establish that the control belongs to your application.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minute| Remedy | Source trust | Component match | Architecture handling | Reversibility |
|---|---|---|---|---|
| Microsoft Visual Basic 6.0 Common Controls update | Official Microsoft package | Provides mscomctl.ocx and comctl32.ocx |
Still requires the registration tool appropriate for a 32-bit legacy control | Can be followed by application repair or removal if needed |
| Application repair or reinstall | The application’s vendor installer | Targets the version expected by that application | The installer may select the required files and architecture | Supported repair or reinstall path |
| Manual registration of an existing, trusted file | A file already supplied by Microsoft or the application vendor | Uses the exact filename and path from the error | Requires a matching 32-bit or 64-bit registration utility | Registration can be undone with the corresponding unregister command |
| Random OCX download | Unverified source | Version and dependency chain are uncertain | Architecture may not match | Replacement can be difficult to diagnose or reverse |
Manual fix: obtain and register the exact OCX
1. Get the component from the correct package
Use the official Microsoft Visual Basic 6.0 Common Controls update when it supplies the filename shown in your message. If the dialog names another control, obtain it from the application’s installer or its vendor’s support channel instead. Keep the package’s original filename and do not rename one OCX to imitate another.
2. Locate the real file
Registration commands operate on a specific file. Identify the full path where the trusted installer placed the OCX. It may be in the application’s installation directory or another location selected by the installer. Do not assume that copying a file into an arbitrary Windows system folder is the right solution.
3. Open an elevated Command Prompt
- Open the Windows Start menu and type Command Prompt.
- Choose Run as administrator.
- Approve the User Account Control prompt if Windows displays one.
Microsoft’s support procedure for COMDLG32.OCX requires an administrative prompt. A non-elevated window can fail even when the file itself is correct.
4. Run the registration sequence against the actual path
For the Microsoft example, run these commands in the elevated window:
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regsvr32 /u Comdlg32.ocxregsvr32 /i Comdlg32.ocx
The commands must point to the real file. If the OCX is not in the current Command Prompt directory, use the full path, for example:
regsvr32 /u "full-path-to-Comdlg32.ocx"regsvr32 /i "full-path-to-Comdlg32.ocx"
Replace Comdlg32.ocx with the exact filename from your dialog only when the application’s vendor or package instructions call for that control. For MSCOMCTL.OCX or another file, use that file’s actual path and follow the package’s registration instructions rather than blindly applying a command intended for a different component.
5. Match the registration utility to a legacy 32-bit control
Visual Basic 6 OCX files are legacy components. On 64-bit Windows, a 32-bit application normally needs the 32-bit version of the registration utility, while a 64-bit application needs the corresponding 64-bit tool. Use the utility and directory specified by the application or component vendor. Windows has separate registration tools, and their directory names do not by themselves tell you which one is correct for your program. Do not copy an OCX into an arbitrary System32 or SysWOW64 folder simply because a web page recommends it.
6. Test the application
Close the Command Prompt, launch the affected application, and reproduce the action that originally displayed Error 339. If it opens normally, the registration addressed the immediate loading failure. Keep the package and the original error text available in case another control is requested later.
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“The system cannot find the file”
The command is pointing to a filename or directory that does not exist. Recheck the spelling, extension, and full path. Locate the file installed by the trusted package, then run the command again with that exact path. Do not respond by downloading a similarly named OCX.
“The module failed to load” or a dependency-related message
This usually means that Windows could not load the OCX itself or one of its dependencies. Verify that the package matches the application, that the control’s architecture matches the registration utility, and that the application vendor’s installer supplied all related files. Registering the same incomplete or incompatible file repeatedly will not add a missing dependency.
An entry-point or procedure error appears
An entry-point-style message can indicate that the file version is not the one expected by the application. Undo the manual replacement if you made one, then use the application’s repair or reinstall process so its installer can restore the intended version. Retain the exact message for the vendor’s support team.
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Access is denied
Close any Command Prompt that was opened without administrative rights and start a new one with Run as administrator. Also close the affected application before registering its control. If an organization manages the computer, its policy may prevent changes to protected locations; ask the administrator to perform the vendor-supported repair.
Registration reports success, but the application still shows 339
Registration success does not confirm that the version, dependency chain, or application installation is correct. Check that the dialog names the same OCX you registered, confirm the file came from the matching package, and verify that the 32-bit or 64-bit tool matches the program. If those checks pass, run the application’s repair option or reinstall it from its original vendor media.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Repair or reinstall the application
When the OCX is present but the error persists, use the application’s own maintenance path before replacing more Windows files. In Windows, open Settings, go to Apps, select the affected program, and use its available Repair, Modify, or Uninstall option. The exact labels vary by installer. If no repair option exists, reinstall from the vendor’s original installer and restart Windows if the installer requests it.
A repair or reinstall is the safer next step when the program was moved between computers, partially removed, updated from an old release, or installed without its supporting controls. It can restore the expected OCX version and other dependencies together instead of leaving a manually registered file that belongs to a different release.
If the application is business-critical, preserve the error text, the OCX filename, Windows edition, and whether registration succeeded before contacting the vendor. Those details distinguish a missing file from a version or dependency problem and prevent support from sending you an unrelated control.
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Windows 10 and Windows 11 notes
The same diagnostic principle applies on Windows 10 and Windows 11: Error 339 identifies a component that the application cannot load, and the filename in the dialog determines the remedy. The operating system version does not turn every 339 message into a COMDLG32.OCX problem. Legacy 32-bit applications may continue to need 32-bit controls and the matching registration utility even when Windows itself is 64-bit.
Do not treat a successful command as a guarantee that an old application is fully compatible with a newer Windows release. If the application still fails after the correct component is installed and registered, the vendor’s repaired or updated installer is the appropriate escalation path.
Quick Recap
Common mistakes that make the problem worse
- Registering the wrong filename:
COMDLG32.OCXandMSCOMCTL.OCXare different controls; one cannot substitute for the other. - Using a random download: an unverified file may be incompatible or incomplete.
- Ignoring architecture: a 32-bit legacy control may need the 32-bit registration utility on 64-bit Windows.
- Running without elevation: Microsoft’s procedure uses an administrative Command Prompt.
- Copying files into arbitrary system folders: location alone does not make a component correct, and it can obscure which version the application is loading.
- Repeating registration after a dependency failure: registration cannot create a dependency that is absent or incompatible.
- Skipping application repair: if the file is the wrong build, the application’s installer is usually the most reliable way to restore the expected component set.
Quick decision checklist
- Read the exact OCX filename in the Error 339 dialog.
- Match that filename to Microsoft’s Visual Basic 6.0 Common Controls update or the application vendor’s installer.
- Locate the file installed by that trusted source.
- Open Command Prompt with Run as administrator.
- Use the registration sequence and the actual file path.
- Use the 32-bit registration utility for a 32-bit legacy control on 64-bit Windows when the vendor specifies it.
- Retry the application.
- If the error remains, treat it as a version, dependency, architecture, or application-installation problem and run the vendor-supported repair or reinstall.
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