>>I created a Innosetup installation program. It attempts to register some DLL (ie. Filer.dll). The setup fails when registers thee DLL with an Unable to register error. I have tried to run the setup as administrator, but get the same error. Is there a trick to getting these DLL to register?
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>I am not sure, if this would be helpful or not, but as far as I remember, Filer.dll is msvcr71.dll and msvcp71.dll dependent

These two are also included in the setup application, and they too fail to register.