Side by Side Configuration Is Incorrect: Fix & Meaning

“Side by side configuration is incorrect” is a Windows error that appears when a program cannot start because its required Visual C++ runtime libraries are missing or mismatched. The fix is usually to reinstall the affected program or the Microsoft Visual C++ Redistributable packages, and in some cases to clear the Windows component store cache. This article explains what causes the error, how to fix it step by step, and how to avoid it in the future.

What Does the Error Mean?

Windows uses a mechanism called side-by-side (SxS) assemblies to manage shared runtime libraries—most commonly the Microsoft Visual C++ Redistributables. Each program declares which version of a runtime it needs in an embedded manifest. When you start the program, Windows checks that the required assembly is present and matches the version and architecture (32-bit vs 64-bit). If the assembly is missing, corrupted, or the manifest is broken, you get:

The application has failed to start because its side-by-side configuration is incorrect.

The error often appears with a reference to the event log, where you can find more details like Microsoft.VC80.CRT or Microsoft.VC90.CRT. Those names point to specific versions of the Visual C++ runtime.

Common Causes

Missing Visual C++ Redistributable – The program needs a runtime that isn’t installed on your system.
Corrupted or partially uninstalled runtime – A failed update or uninstall can leave broken registry entries.
Wrong architecture – A 64-bit program may require the 64-bit runtime, but only the 32-bit version is installed (or vice versa).
Damaged program installation – The program’s own files or manifest are corrupted.
System file corruption – Windows component store or system files are damaged.
Antivirus interference – Some security software may quarantine or block runtime DLLs.

How to Fix the Error

Try the fixes in order. Most users resolve the issue with the first two steps.

Reinstall the program – Uninstall the affected application, restart your PC, and install it again. This often restores the correct runtime files.
Install the latest Microsoft Visual C++ Redistributable – Download the official package from Microsoft’s website (search for “Visual C++ Redistributable latest supported downloads�). Install both the x86 and x64 versions, even if you think you only need one.
Repair the Visual C++ Redistributables – Open Control Panel > Programs and Features, find each “Microsoft Visual C++� entry, click Change, then select Repair. Do this for every version listed.
Check the Windows Event Log – Press Win + R, type eventvwr, and look under Windows Logs > Application for errors with source “SideBySide�. The error details will tell you exactly which assembly is missing.
Run System File Checker – Open Command Prompt as administrator and run sfc /scannow. This repairs corrupted system files that may affect the runtime.
Clear the Windows component store cache – In an elevated Command Prompt, run Dism /Online /Cleanup-Image /RestoreHealth, then sfc /scannow again.
Reinstall the runtime manually – If the event log shows a specific version like Microsoft.VC80.CRT, download that exact redistributable package (e.g., Visual C++ 2005 for VC80) and install it.

How to Prevent It in the Future

Keep Windows updated – Windows Update often includes runtime updates.
Install all Visual C++ Redistributables – It’s safe to have multiple versions installed; they don’t conflict.
Always install programs from trusted sources – Corrupted installers can break manifests.
Don’t manually delete or move runtime DLLs – Programs expect them in specific locations.
Create a system restore point before installing new software, so you can roll back if something goes wrong.

What If the Error Persists?

If you’ve tried all the above and the error still appears, consider these steps:

Check for a 32-bit vs 64-bit mismatch – If the program is 32-bit, it needs the x86 runtime; if it’s 64-bit, it needs the x64 runtime. Install both to be safe.
Use a clean boot – Temporarily disable startup programs and non-Microsoft services to see if a background app is interfering.
Reinstall the program with administrator rights – Right-click the installer and select “Run as administrator�.
Look for a program-specific patch – Some older games or business apps have known issues; check the developer’s support page.
Consider a system restore – If the error started recently, restoring to an earlier point may help.

If none of these work, the issue may be a deeper system corruption. Back up your data and consider using Windows’ “Reset this PC� feature, which reinstalls Windows while keeping your files.

Frequently Asked Questions

Can I ignore this error and use the program anyway?

No. The error means the program cannot start because it lacks required runtime components. Without them, the program will not run.

Do I need to install every Visual C++ Redistributable?

It’s not mandatory, but it’s safe and often helpful. Different programs use different versions, and having them all installed prevents this error for most software.

Why does the error mention “side by side� if I only installed one program?

“Side by side� refers to how Windows stores multiple versions of the same runtime library. The program you installed expects a specific version that isn’t present, so Windows can’t find a compatible assembly.

Is this error dangerous or a sign of a virus?

No, the error itself is not dangerous. It’s a common Windows message caused by missing runtime files. However, if you downloaded the program from an untrusted source, you should scan it with antivirus software.

Will reinstalling Windows fix it?

Yes, a clean Windows installation will include all default runtimes and remove any corruption. But try less drastic fixes first, as they usually work.

Does this error affect Windows 10 and Windows 11?

Yes, it can occur on any modern Windows version, including Windows 10 and 11. The fixes are the same.

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