Fix FORMATETC (0X80040064) Invalid Structure Error on Windows

Corrupted Clipboard Data or Viewer Chain

If you're hitting the 0x80040064 FORMATETC error when copying or pasting, nine times out of ten it's a corrupted clipboard viewer chain. I know this error is infuriating—you're just trying to move a file or image, and Windows throws up this cryptic nonsense. The real trigger? A third-party clipboard manager, a stuck clipboard viewer, or even a misbehaving explorer.exe session that's holding onto a bad FORMATETC structure.

Here's the fix that works for 90% of people:

1. Press Win + R, type cmd, and hit Enter.
2. In the Command Prompt, run:

   echo off | clip

   This clears the clipboard and resets the internal data format structure. Yes, it's that simple.
3. Restart Explorer: open Task Manager (Ctrl + Shift + Esc), find Windows Explorer, right-click it, and choose Restart.

That usually kills the bad FORMATETC entry. If the error keeps coming back (like it did on my Windows 11 machine last month), you've got a stuck clipboard viewer. Open regedit and check this key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Clipboard

If you see a ViewerChain value with junk in it (like a path to an old clipboard tool you uninstalled), delete it. Reboot. Done.

Missing or Corrupt COM Registration

When the clipboard fix doesn't work, the error often comes from a broken COM component. This happened to me on Windows 10 22H2 after a botched Office update. The FORMATETC structure is a COM type—think of it as a contract between applications about what data format they're passing. If a COM server (like Ole32.dll) gets its registration corrupted, the structure validation fails with 0x80040064.

To fix it, re-register the core COM libraries. Open an elevated Command Prompt (right-click > Run as administrator) and run these commands in order:

regsvr32 /u ole32.dll
regsvr32 ole32.dll
regsvr32 /u oleaut32.dll
regsvr32 oleaut32.dll
regsvr32 /u olepro32.dll
regsvr32 olepro32.dll
regsvr32 /u comctl32.dll
regsvr32 comctl32.dll

Yes, it's tedious. Yes, it works. I've seen this kill the error on systems where nothing else did. After re-registering, reboot. If the error pops up in a specific app (like Photoshop or Word), reinstall that app's COM components by running its repair installer—Microsoft Office has a built-in repair in Apps & Features.

One more thing: check for a missing OLE32.DLL in C:\Windows\System32. If it's gone or zero bytes, you've got bigger problems—run sfc /scannow from an admin prompt, then DISM /Online /Cleanup-Image /RestoreHealth.

Malformed Data Format in Drag-and-Drop Operations

This one's niche but real. If you only see 0x80040064 when dragging files between Explorer windows, or into a browser like Chrome or Firefox, the issue is a flawed FORMATETC structure created by a shell extension. I wasted two hours on this once—turned out a Dropbox overlay handler was passing a null ptd (target device) pointer in the FORMATETC struct. Windows 11 22H2 doesn't like that at all.

The fix: disable non-Microsoft shell extensions. Use Autoruns from Sysinternals (free, from Microsoft). Run it, go to the Explorer tab, and uncheck everything that isn't signed by Microsoft or your primary cloud provider (OneDrive, Google Drive, Dropbox). Reboot. Then test drag-drop.

If the error stops, enable extensions one by one until you find the culprit. Common offenders: old WinRAR context menus, NVIDIA shell extensions, and any "send to" handler from a tool you installed years ago. Delete that extension's registry entry in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved—remove the key for that CLSID. Don't just uncheck it in Autoruns; remove it from there.

Quick-Reference Summary

If none of these work—and I've only seen that once in six years—run a Windows repair install using the Media Creation Tool. That replaces all system files without touching your apps. But start with the clipboard fix. It's almost always that.