HDC hDC = GetDC(m_hWndDesktop);
 if(hDC)
 {
    RECT rc;
    rc.left = m_nCurrentX;
    rc.top = m_nCurrentY;
    rc.right = m_nCurrentX+15;
    rc.bottom = m_nCurrentY+15;

    // 15 is for a little drift at the bottom of the desktop
    int nTestHeight = m_nScreenHeight - 15; 
    
    // redraw the desktop window right away
    if(m_nCurrentY// snow drift here
        RedrawWindow(m_hWndDesktop, &rc, NULL, RDW_INVALIDATE 
            | RDW_ERASE | RDW_UPDATENOW );

     // ....

    m_nCurrentX += m_nIncrement;

    if(m_nCurrentY>m_nScreenHeight)
    {
        m_nCurrentY = 0;
        m_nCurrentX = abs(rand()*m_nScreenWidth/RAND_MAX);
        if(abs(rand()*100/RAND_MAX)>50)
            m_bIsBigFlake = TRUE;
        else
            m_bIsBigFlake = FALSE;
    }

   // ...

    HPEN pOldPen = (HPEN)SelectObject(hDC, m_hFlakePen);

   // ....

    // specify RDW_NOERASE to keep the desktop from drawing the background
    if(!m_bIsVista)
    {
        if(!m_bOverIcons && m_nCurrentY// Restore DC settings to their original values
    RestoreDC(hDC, storedDC);

    // Release the DC
    ReleaseDC(m_hWndDesktop, hDC);
 }