Extension Host failed to load extension DLL

Hi Everyone,

I am new to NPS. I am using Windows Server 2008 R2. I have developed an Authentication Extension DLL which is basically a MFC Extension DLL for custom authentication in NPS. (http://msdn.microsoft.com/en-us/library/windows/desktop/bb892024(v=vs.85).aspx)

Now, to apply this Extension DLL at NPS I have used following steps:- 

1. I have put that DLL in %System Root%\System32\radius.dll folder.
2. I have create HKLM\System\CurrentControlSet\Services\AuthSrv\Parameters\registry key and set path of DLL as described here http://msdn.microsoft.com/en-us/library/windows/desktop/bb892024(v=vs.85).aspx

Now, when I am restarting NPS server I am getting following error:-

"Extension Host is failed to load DLL.Path %System Root%\System32\radius.dll".