Register a dll in x64

Same problem for me :(
I don't understand how to "save" or "activate" them once they're in both folders, what is the exact command to do in "Run"
For the horse's rapunzel: I can't run the program under something .... because it's for installing a program that I'm missing this < .dll >
(And I've read the whole conversation several times and tried everything described!)

Hi, if you look a little you'll find this:

When you attempt to run Regsvr32.exe to register a 32-bit DLL file in a 64-bit version of Windows, the following error message appears:
file_name.dll is not a valid executable file and no registration helper is registered in the registry for this type of file.
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CauseThis problem occurs because the Regsvr32.exe file in the System32 folder is...This problem occurs because the Regsvr32.exe file in the System32 folder is a 64-bit version. When you run Regsvr32 to register a DLL file, you are using a 64-bit version by default.
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ResolutionTo resolve this problem, run Regsvr32.exe from the %SystemRoot...To resolve this problem, run Regsvr32.exe from the %SystemRoot%\Syswow64 folder. For example, type the following command in the Start menu\Run to register the DLL file:

\windows\syswow64\regsvr32 c:\file_name.dll
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StatusThis behavior is by design of the product.This behavior is by design of the product

from here: https://support.microsoft.com/fr-fr/help/249873/how-to-use-the-regsvr32-tool-and-troubleshoot-regsvr32-error-messages

I have this problem trying to register an MPC dll to get the EAC audio filter..but it returns an error message "the DLL was loaded but the call to DllRegister failed with error code 0x80070005"
so I keep searching..
bye

Thank you, Corben, it works perfectly with the manual copy in syswow64 and system32.