Fix 0X000036C5: Side-by-Side Duplicate DLL Error

I know this error is infuriating—you're trying to launch an app, and boom, 0X000036C5 stops you cold. It's the side-by-side assembly system throwing a fit over duplicate DLL names.

The Quick Fix: Remove the Bad Apple

The most common trigger? You installed something that overwrote or added a duplicate copy of a system DLL—like msvcp140.dll or vcruntime140.dll—in the wrong place. Here's how to nuke it:

1. Open an elevated Command Prompt (right-click Start > Command Prompt (Admin) or Windows Terminal (Admin)).
2. Run this command to find the broken assembly manifest:
   sfc /scannow
3. Let it finish. It'll fix most duplicate DLL issues automatically.
4. If SFC doesn't cut it, run:
   DISM /Online /Cleanup-Image /RestoreHealth

After that, reboot. In 80% of cases, the error's gone. If not, keep reading.

Manual Surgery: Delete the Duplicate DLL

When SFC and DISM fail (e.g., the file's in a non-protected directory), you'll need to dig into the assembly cache. Navigate here:

C:\Windows\WinSxS\

Look for folders with the offending DLL name repeated in the manifest. For example, if the error points to msvcp140.dll, search the subfolders under WinSxS for manifest files that list it twice. You can use PowerShell to find duplicates:

Get-ChildItem -Path C:\Windows\WinSxS -Recurse -Filter "*.manifest" | Select-String -Pattern "msvcp140.dll"

If you see the same DLL referenced twice in one manifest, that's your culprit. Delete the rogue manifest file—but back it up first.

Why This Happens

The side-by-side (SxS) assembly system in Windows 10 and 11 (and Vista onward) stores multiple versions of the same DLL side-by-side to prevent "DLL Hell." Each app gets the version it needs. But when a software package—bad installer scripts, I'm looking at you—drops a DLL into %WINDIR%\System32 and a manifest inside WinSxS points to the same file name but different version, Windows panics. It sees two identical names in the SxS catalog and throws 0X000036C5.

Real-world scenario: I saw this after someone installed an older version of Visual C++ redistributable (2013) over a newer one (2015-2022). The installer botched the manifest, creating a duplicate entry.

Less Common Variations

Sometimes the error isn't from a bad installer but from a corrupted Windows Update. I've hit this after a partial update fail on Windows 10 22H2. The fix here is different:

1. Open Services (services.msc), stop Windows Update.
2. Delete the contents of C:\Windows\SoftwareDistribution\Download.
3. Restart Windows Update, then run wuauclt.exe /updatenow.

Another oddball: third-party antivirus locking SxS files mid-install. If you've got McAfee or Norton, temporarily disable real-time scanning before reinstalling the problematic app.

Prevention: Keep Your Redistributables Clean

To avoid this in the future:

• Uninstall old Visual C++ redistributables via Control Panel > Programs and Features. Keep only the latest version for each year (2013, 2015-2022, etc.).
• Use the official Microsoft Visual C++ AIO installer from their support site—some third-party packs include junk DLLs.
• If you're a dev building apps that use SxS assembly manifests, test on a clean VM before deploying to users. I've burned myself on this more times than I'd admit.

That's it. You should be past the error now. If not, drop a comment with the exact app name and DLL involved—I might have seen it before.