LPARAM lParam = 0; //param to use
EnumWindows( EnumWindowsProc, lParam); //usage
BOOL CALLBACK EnumWindowsProc( HWND hWnd, LPARAM lParam )
{
//This function will be called on each Window!
// return FALSE to stop enumeration
EnumChildWindows(hWnd, EnumWindowsProc, lParam); //You can enumerate child windows too
return TRUE; //continue enumeration
}