System.Reflection.Assembly.LoadFile - " is not a valid Win32 application. (Exception from HRESULT: 0x800700C1)"

In my code, I want to create dinamically an istance to an assembly using :

System.Reflection.Assembly myDllAssembly = System.Reflection.Assembly.LoadFile(targetdllpath);

If my target dll is compiled as "AnyCPU", it works succesfully.

Now, I have to compile my target DLL as X86 because it must to use a COM object.

So, LoadFile method returns this error:

" is not a valid Win32 application. (Exception from HRESULT: 0x800700C1)"

Can you help me?