Virtual Function and ZeroMemory

What caused me to write this post is a BUG. Really i am not joking.. Everyone know that there is a virtual table pointer is present at the  beginning of the object memory . i am also know that.. But i did a mistake long ago. Following lines shows it...

class Base

{

public :

   virtual void Render()

   {
   }

};

class Derived: public Base

{

    // i have several data members here..

public :

    Derived()

    {

        // For easily initializing all of my data members to zero , i used ZeroMemory here

       ZeroMemory(this,sizeof(Derived));

       // Danger .. This also clear the virtual table pointer..

    }

   void Render()

   {

   }

};

So when i called it like 

Derived *d = new Derived()

d->Render();

it crasheddd .... because of the ZeroMemory in the constructor set the vptr to Zero.