I want to use Graphviz + Doxygen to generate a class diagram based on C++ code. This works already as Doxygen comes with a native DOT suppo
I had similar problem its successfully solved now.
Following are the steps(assuming that you are using GUI version of Doxygen-Doxywizard)
Click on Expert button
Go to Dot tab and select the DOT_PATH. Browse the folder where you have installed the program. e.g., " C:/Program Files (x86)/Graphviz2.32/bin "
Hope it helps, Anit