You can try the following raw WSTP/MathLink command:
knl = LinkLaunch[ "C:\\Program Files\\Wolfram Research\\Mathematica\\9.0\\MathKernel" <> " -noprompt -subkernel -noinit -mathlink -noicon "];
safeRead := If[LinkReadyQ[knl], LinkRead[knl]]
If you have everything right, you shall have a result like
Using the windows resource monitor, you can verify the new kernel by looking at the process ID/PID
LinkWrite[knl, Unevaluated[$ProcessID]] (*evaluated directly with a sub-kernel*)
$ProcessID (*evaluated directly with default kernel*)
Try the code above and lets see what do you have.
One thing you may have to modify is the exact location of the installation of the Wolfram Desktop product. In my case I do have the version 9 installed in
C:\\Program Files\\Wolfram Research\\Mathematica\\9.0\\MathKernel
That is why it appears in my code. You will have to check the installation location by yourself.