How to Fix Atl100.dll Not Found or Missing Errors

If installing the MFC security update doesn't fix the error, reinstall the program that uses the file

Atl100.dll errors are caused by situations that lead to the removal or corruption of the atl100 DLL file. In some cases, atl100.dll errors could indicate a registry problem, a virus or malware issue, or even a hardware failure.

Microsoft calls this file ATL Module for Windows.

The atl100.dll error message could apply to any program or system that might utilize the file on any of Microsoft's operating systems, including Windows 11, Windows 10Windows 8Windows 7Windows VistaWindows XP, and Windows 2000.

Atl100.dll Errors

ATL100 DLL error message in Windows

There are several ways atl100.dll errors can show up on your computer. Here are some of the more common error messages you might see:

  • Atl100.dll Not Found
  • This application failed to start because atl100.dll was not found. Re-installing the application may fix this problem.
  • Cannot find [PATH]\atl100.dll
  • The file atl100.dll is missing.
  • Cannot start [APPLICATION]. A required component is missing: atl100.dll. Please install [APPLICATION] again.

The context of the error is an important piece of information that will be helpful while solving the problem. 

Atl100.dll error messages might appear while using or installing certain programs (such as a Microsoft Office product) or games (like Scarlet Blade), or when Windows starts or shuts down.

How to Fix Atl100.dll Errors

Follow these steps in the order they're given below to try the more likely fixes first.

Do not download atl100.dll from a "DLL download" website. There are many reasons why downloading a DLL file like that is a bad idea. If you need a copy of this file, it's best to obtain it from its original, legitimate source.

  1. Download and install the Microsoft Visual C++ 2010 Service Pack 1 Redistributable Package MFC Security Update. This will replace/restore the atl100.dll with the most recent copy provided by Microsoft.

    You're given a few download options, based on the version of Windows you have installed—x86 (32-bit) or x64 (64-bit).

    Start Windows in Safe Mode to complete any of these steps if you're unable to access Windows normally due to the error.

  2. Restore the file from the Recycle Bin. The easiest possible cause of a "missing" atl100.dll file is that you've mistakenly deleted it.

    If you suspect this, but you've already emptied the Recycle Bin, you may be able to recover the file with a free file recovery program.

    This step is smart only if you're confident you've deleted the file yourself and that it was working properly before you did that (i.e., it wasn't malicious or corrupt).

  3. Run a virus/malware scan of your entire system. Some atl100.dll errors could be related to a virus or other malware infection on your computer that has damaged the DLL file. It's even possible that the error you're seeing is related to a hostile program that's masquerading as the file.

  4. Use System Restore to undo recent system changes. If you suspect that the error was caused by a change made to an important file or configuration, a System Restore could solve the problem.

  5. Reinstall the program that's producing the error. If the atl100.dll error occurs when you use a particular program, reinstalling that program might help.

  6. Install any available Windows updates. Many service packs and other patches replace or update some of the hundreds of Microsoft distributed DLL files on your computer. The atl100.dll file could be included in one of those updates.

  7. Test your memory and then test your hard drive. We've left the majority of hardware troubleshooting to the last step, but your computer's memory and hard drive are easy to test and are the most likely components that might cause atl100.dll errors as they fail.

    If the hardware fails any of your tests, replace the memory or replace the hard drive as soon as possible.

  8. Repair your installation of Windows. If the individual atl100.dll file troubleshooting advice above is unsuccessful, performing a startup repair or repair installation should restore all Windows DLL files to their working versions.

  9. Use a free registry cleaner to repair atl100.dll related issues in the registry. A free registry cleaner program may be able to help by removing invalid registry entries that might be causing the DLL error.

    We rarely recommend using registry cleaners (see our Registry Cleaners FAQ for more on when to use one). They're included here as a "last resort" attempt before the destructive step coming up.

  10. Perform a clean installation of Windows. This will erase everything from the hard drive and install a fresh copy of Windows. If none of the steps above correct the atl100.dll error, this should be your next course of action.

    All the information on your hard drive will be erased during this step. Make sure you've made the best attempt possible to fix the error using a troubleshooting step prior to this one.

  11. Troubleshoot for a hardware problem if any errors persist. After a clean installation of Windows, the DLL problem can only be hardware related.

Need More Help?

If you're not interested in fixing this problem yourself, see How Do I Get My Computer Fixed? for a full list of your support options, plus help with everything along the way like figuring out repair costs, getting your files off, choosing a repair service, and a lot more.

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