Assistance with ISAPI-DLL

Hello,

I'm having some difficulty being to able access/execute DLLs within a website on IIS 8 / Windows 2012 R2.

I currently have a main website:

dev.domain.com

with the dll files located in a virtual directory (alias web) under the main website.

When I try to access any of the dlls by url:

http://dev.domain.com/web/cgi-bin/logindll.dll

I receive the following message: The resource you are looking for does not exist!

I've checked that the virtual directory has Read/Script/Execute permissions for CGI and ISAP-DLL in Handler Mappings.

Are there other steps required to configure ISAPI DLL?

Thanks