nt下的视频捕获怎么会死机？？？请高手解答！(200分)

我用vfw编些了一个小程序，可是点了两下按键，程序就死了！源程序如下：
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
ExtCtrls, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
Panel1: TPanel;
Button2: TButton;
procedure FormCreate(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
wndCap: HWND;
wndCap1: HWND;

implementation
uses vfw;

{$R *.DFM}

procedure TForm1.FormCreate(Sender: TObject);
begin

wndCap := capCreateCaptureWindow('capPhoto', WS_CHILD or WS_VISIBLE, 0, 0,
panel1.Width , panel1.Height , panel1.Handle, 0);

SendMessage(wndCap, WM_CAP_DRIVER_CONNECT, 0, 0); // 连接到第一个视频卡
SendMessage(wndCap, WM_CAP_SET_SCALE, WParam(true), 0); // 设为充满wndCap窗口
SendMessage(wndCap, WM_CAP_SET_PREVIEWRATE, 30, 0); // 设置速度
capoverlay(wndcap,true);


end;

procedure TForm1.Button2Click(Sender: TObject);
begin
panel1.height:= panel1.height-10;
panel1.width:=panel1.width-10;
capdriverdisconnect(wndCap);
wndCap := capCreateCaptureWindow('capPhoto', WS_CHILD or WS_VISIBLE, 0, 0,
panel1.Width , panel1.Height , panel1.Handle, 0);
SendMessage(wndCap, WM_CAP_DRIVER_CONNECT, 0, 0); // 连接到第一个视频卡

SendMessage(wndCap, WM_CAP_SET_SCALE, WParam(true), 0); // 设为充满wndCap窗口
SendMessage(wndCap, WM_CAP_SET_PREVIEWRATE, 30, 0); // 设置速度
capoverlay(wndcap,true);
end;

end.
请高手帮我分析一下，哪有问题？

请问用的那种卡

是philps的saa7146卡