Difference between win32 dll and .net dll in the context of web application?

My web application, written in WPF( XBAP), p/invokes a win32 dll (player.dll written in C and C++). I deployed the application. When I tried running the web-application in IE, initially I got this error:

System.DllNotFoundException: Unable to load DLL 'Player.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)

But when I manually copied my win32 dll to C:\Windows\System32 of t开发者_如何学JAVAhe client PC, it worked, even though my web application uses several other .Net dlls and I didn't copy them manually.

So I'm confused as to why exactly do I need to copy only win32 dll to the client PC, while not .Net dlls? Do web-applications access them differently?

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The related topic is this :

DllNotFoundException when web application p/invokes a win32 DLL

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The rules to locate assemblies (.NET) are not the same as for locating native DLLs. Here are the two rule sets:

• Assemblies: http://msdn.microsoft.com/en-us/library/yx7xezcf.aspx
• Win32 DLLs: http://msdn.microsoft.com/en-us/library/ms682586(v=vs.85).aspx