NetMeeting and DirectX application will not work at the same time

I use the following code in my application that uses DirectX to draw images. Also, I want to use NetMeeting to make an audio call. So, I start NetMeeting and the moment I start it, the images are lost in my application, and further on I am unable to view images. I have to restart my application.

I use the following C++ code to find the driver capability for overlay support. The last condition fails only if I start NetMeeting. Otherwise it works fine. What does NetMeeting have to do disable the driver capability for overlay? How can this be countered?

/*****************/
DDCAPS  capsDrv;
HRESULT ddrval;
INIT_DIRECTDRAW_STRUCT(capsDrv);
ddrval = g_lpdd->GetCaps(&capsDrv, NULL);
if (FAILED(ddrval))
{
return FALSE;
}
if (!(capsDrv.dwCaps & DDCAPS_OVERLAY))
{
return FALSE;
}

/*******************/

Thanks.