I'm not sure if this is the right forum for XAudio2 questions,it was in the DirectX SDK...so the problem is this:When I implement the XAudio2Sound3D sample from the June 2010 SDK.I pretty much copied it all in my own framework and this one variable(sound3DInstance) shows up as an unresolved external: X3DAudioCalculate(sound3DInstance, &listener, &emitter, calcFlags, &dspSettings); and X3DAudioInitialize(details.OutputFormat.dwChannelMask, SPEEDOFSOUND, sound3DInstance);
Where the variable types are:

X3DAUDIO_HANDLE sound3DInstance;
X3DAUDIO_LISTENER listener;
X3DAUDIO_EMITTER emitter;
X3DAUDIO_DSP_SETTINGS dspSettings;
DWORD calcFlags = X3DAUDIO_CALCULATE_MATRIX | X3DAUDIO_CALCULATE_DOPPLER | X3DAUDIO_CALCULATE_LPF_DIRECT | X3DAUDIO_CALCULATE_LPF_REVERB | X3DAUDIO_CALCULATE_REVERB;
const float SPEEDOFSOUND = X3DAUDIO_SPEED_OF_SOUND;
XAUDIO2_DEVICE_DETAILS details;

Now the only common variable in both functions that show the error is sound3DInstance,so that has to be the problem.In the SDK Sample all the variables are put in a struct called AUDIO_STATE and in the initialization of the program,they call:
ZeroMemory( &g_audioState, sizeof( AUDIO_STATE ) );
In my code the variables are members of my Sound class and I just ZeroMemory them one by one,so shouldn't the effect be the same?

That's because you have to link to their corresponding libraries. Try this:

#pragma comment(lib, "x3daudio")
#pragma comment(lib, "xaudio2")