Find and Open a File on Remote Computer

I have a file on one server(Windows 2003) and need to access from another server (IIS server - Windows 2008) , I have written the program for the same which works fine and I can access the file.

But when this comes to the DLL (which registered successfully on Windows 2008), its not able to find the file on Windows 2003.

What could be possible reasons, please help !!!

Thanks in advance!