JNI-invocation API problem - Java

Does anyone managed to launch a java VM from a MS VC++ application?
I'm trying access my java classes from the C++ side, but I can't. The
problem appears when invoking the method JNI_CreateJavaVM(..), that always
returns -1.

I've surf the web and the fora, and I've tried all the solutions and
different implementations I've found. In theory, the code is quite simple,
and in this first step, I'm not loading any of my java classes but only
starting a clean VM.

My details are:
VC++ in Visual Studio. NET
Sun Java SDK 1.4.06

One of my firsts doubts is: Do I have to use the jvm.dll that comes with the
jre of the sdk, or I can simply use the jvm.lib ?
Also, I suspect the problem comes from the fact that I have different VM in
my computer, Can any of briefly explain me how does JNI finds and starts the
VM?

I haven't attached any code because I've tryied many different solutions.
Thank to all of you in advance