Fix 0x800401C3: CONVERT10 OLE Stream Bitmap Error

This error hits when Windows can't convert a bitmap stored in an OLE stream. It usually shows up during drag-and-drop or clipboard paste. Here's the real fix.

What's actually happening when you see 0x800401C3

You're dragging a picture from Outlook into Word, or pasting a screenshot from Snipping Tool into Excel, and instead of the image appearing, you get a dialog: "CONVERT10_E_OLESTREAM_BITMAP_TO_DIB (0x800401C3)". Or maybe it happens when your app tries to load an embedded OLE object that contains a bitmap. The common thread is that Windows is trying to convert a bitmap stored in an OLE stream format (the legacy presentation format) into a device-independent bitmap (DIB), and it can't.

I've seen this most often on Windows 10 22H2 and Windows 11 23H2 after a round of updates, particularly when the app doing the copy is 32-bit and the target is 64-bit (or vice versa). It also shows up in custom line-of-business apps that use the old OLE clipboard formats from the Windows 95 era. The error isn't random; it's a specific COM failure, HRESULT 0x800401C3, which maps to CONVERT10_E_OLESTREAM_BITMAP_TO_DIB.

The root cause in plain English

OLE (Object Linking and Embedding) has been around since Windows 3.1. When an app copies a bitmap to the clipboard, it can offer it in several formats: CF_BITMAP, CF_DIB, or a more complex OLE stream that wraps the bitmap inside a STGMEDIUM structure. The stream format is convenient for OLE embedding because it carries extra metadata (palette, dimensions, etc.). But not every app can read the stream format. When the receiving app asks Windows to convert that OLE stream bitmap into a plain DIB, Windows calls the OLE conversion routine. If the stream is malformed, if the source app closed the stream prematurely, or if there's a mismatch in the OLE subsystem (like a broken registry entry for the bitmap handler), the conversion fails with 0x800401C3.

The reason step 3 works is that re-registering the OLE libraries resets the conversion handlers. The reason the clipboard clear in step 2 helps is that a stale clipboard entry can hold a corrupted stream. And the reason a clean boot in step 4 matters is that third-party clipboard managers (looking at you, older versions of ClipboardFusion and Ditto) hook into the OLE clipboard and can mangle the stream before Windows sees it.

How to fix it

Close all Office apps and any app that uses OLE. That means Word, Excel, Outlook, PowerPoint, and also any custom apps that embed objects. The OLE conversion happens in-process, so if the app is running, the fix won't stick.
Clear the clipboard completely. Open an elevated Command Prompt and run:
```
cmd /c "echo off | clip"
```
This empties the clipboard. If you have a clipboard history tool, clear its history too.
Re-register the OLE DLLs. In an elevated Command Prompt, run these one at a time:
```
regsvr32 /s ole32.dll
regsvr32 /s oleaut32.dll
regsvr32 /s actxprxy.dll
regsvr32 /s comcat.dll
```
You won't see a confirmation because of the /s switch, but if you omit it, you should see a success dialog. If any fail, note the error.
Check for third-party clipboard managers. Disable or uninstall them temporarily. Common culprits: Ditto, ClipboardFusion, ArsClip, and even some remote desktop tools that sync clipboards. Reboot after disabling.
Run a System File Checker scan. OLE corruption can come from a bad system file. Run:
```
sfc /scannow
```
Then run DISM to repair the image:
```
DISM /Online /Cleanup-Image /RestoreHealth
```
Test with a clean boot. Use msconfig to disable all non-Microsoft services and startup items, then reboot. If the error disappears, you've got a third-party conflict. Re-enable services in batches to find the culprit.

If it still fails after all that

There are a few less common causes. One is a corrupted user profile. Create a new local admin account, log in, and try the same copy-paste. If it works there, your old profile has a broken OLE registration in HKCU\Software\Classes. You can try exporting the relevant keys from the new profile and importing them, but honestly, migrating to a new profile is often faster.

Another possibility: the source app is using an old version of the OLE libraries. If you're dealing with a custom app built with Visual Basic 6 or an early .NET version, it might be linking against a deprecated OLE DLL. In that case, the fix is on the app developer's side—they need to use OleConvertOLESTREAMToIStorage with a proper FORMATETC structure. You can't fix that from the OS.

Finally, check the event log. Look under Windows Logs > Application for errors from source "Application Error" or "Microsoft-Windows-COMRuntime". The details often name the exact DLL that failed. If it's a third-party DLL, update or remove the software that owns it.

One more thing: if you're on Windows 11 24H2, there was a known issue with OLE clipboard operations in build 26100.1742 that Microsoft fixed in KB5043145. Make sure you're patched.