Fix STATUS_SXS_VERSION_CONFLICT 0XC0150009 on Windows

You're launching a program — maybe an older game, a business app, or some custom software — and instead of starting normally, you get a popup with error code 0xC0150009. The message says something about a side-by-side configuration or a version conflict. I've seen this happen most often with Adobe Creative Suite 3 or 4, older versions of Visual Studio, or custom .NET apps built against a specific runtime. It's infuriating because the app just sits there, refusing to load, with no real clue why.

Root cause

Windows uses a feature called Side-by-Side (SxS) to manage DLL versions. Instead of every app dumping its DLLs into system32, each app has a manifest that tells Windows exactly which version of a shared library (like MSVCR90.dll or MSVCP100.dll) to load. When the manifest says "I need version 9.0.30729.6161" but your SxS store only has version 9.0.30729.4148, you get this error.

The trigger? Usually a botched update, an incomplete uninstall of a Visual C++ Redistributable, or installing a newer version of an app that overwrites the shared assembly without updating the manifest correctly. The error code 0xC0150009 literally means the loader couldn't find the exact version of a required assembly in the SxS store. It's not a "corrupted file" problem — it's a version mismatch problem.

Fix: Step-by-step

Start with the simplest fix — it works 80% of the time. Skip the registry edits and sfc /scannow until you've tried this.

Identify the conflicting DLL. Open Event Viewer (eventvwr.msc), go to Windows Logs > Application, and look for a warning or error from SideBySide (source: "SideBySide"). The details will list the failing assembly — often something like Microsoft.VC90.CRT,version="9.0.21022.8". Note the version number.
Reinstall the correct Visual C++ redistributable. Go to Microsoft's official redistributable page. Download the version matching the failing assembly: e.g., for VC90 (Visual Studio 2008), download the Visual C++ 2008 redistributable. For VC100, download Visual C++ 2010. Install both x86 and x64 versions if your app is 32-bit (most older apps are).
Repair the SxS store manually. If reinstalling doesn't work, open Command Prompt as Administrator and run:
```
dism /online /cleanup-image /restorehealth
sfc /scannow
```
This checks system file integrity and fixes the store. Reboot after.
Check for a corrupt manifest in the app folder. Go to the app's installation directory. Look for a file like app.exe.manifest or a Microsoft.VC90.CRT.manifest in the app's folder. Open it in Notepad. If the version string doesn't match what's in the SxS store (you can check C:\Windows\WinSxS\ for installed assemblies with dir /b Microsoft.VC90*), edit the manifest to match an existing version. Be careful — this is a hack, not a permanent fix. Better is to reinstall the app.
Use the SxS troubleshooting tool. Download the SxsTrace utility from Microsoft. Run:
```
sxstrace trace -logfile:sxs.etl
sxstrace parse -logfile:sxs.etl -outfile:sxs.txt
```
Then open sxs.txt — it shows exactly which assembly is missing or mis-versioned. This pinpoints the problem so you can fix it with the right redistributable.

If it still fails

Sometimes the app itself is the problem — it was compiled against a very specific build of a library that Microsoft no longer redistributes (like the 2005 SP1 ATL fix). In that case, try these workarounds:

Run the app in compatibility mode for an older Windows version (e.g., Windows 7 or Windows XP SP3). Right-click the .exe, go to Properties > Compatibility, check "Run this program in compatibility mode for", and choose an older OS.
Use Process Monitor (procmon.exe) to filter by the app name and look for NAME NOT FOUND results. This shows you exactly which file it's trying to load and where it's looking. Often the app needs a DLL placed in its own folder, and the manifest is wrong.
Reinstall the app using an installer that includes the correct redistributables. Sometimes the original installer is damaged.

In my experience, the reinstall of the matching Visual C++ redistributable solves 90% of these cases. The rest are usually old games or niche business apps that need a compatibility shim. If you're still stuck after all this, post the SxsTrace output in a forum — someone will spot the mismatch quickly.