Knowing what you are talking about, before talking. is always a good start.
Only DLL files which add additional features to the shell are required to be registered. Dependancy DLL's for Visual C and other lib runtimes to not need to be registered with the system as they are automatically loaded by the windows dll loader as long as they are in.
1. Program's root directory.
2. Windows\System
3. Windows \System32
That you posted this to a 8+ month old thread.....