why I can not hook the interrupt?

I copied a small VxD from a book , the codes are below.
I dont know why i can not hook the interrupt, who can help me?

____________________the code____________________
//mouse.h
#include <vtoolscp.h>
#include <vdw.h>
#define DEVICE_CLASS MouseDevice
#define MOUSE_DeviceID UNDEFINED_DEVICE_ID
#define MOUSE_Init_Order UNDEFINED_INIT_ORDER
#define MOUSE_Major 1
#define MOUSE_Minor 0
#define IRQ_3 3 //com2
KTrace T("mouse");   //debugger

class MouseInt : public VHardwareInt
{
public:
MouseInt();
virtual VOID OnHardwareInt();
};

class MouseDevice : public VDevice
{
public:
virtual BOOL OnSysDynamicDeviceInit();
virtual BOOL OnSysDynamicDeviceExit();
MouseInt *pMyInt;
};
-------------------the code----------------------
// MOUSE.cpp - main module for VxD MOUSE

#define DEVICE_MAIN
#include "mouse.h"
Declare_Virtual_Device(MOUSE)
#undef DEVICE_MAIN

PDWORD pVal=(PDWORD)0x9fffc;//buffer for counting
BOOL MouseDevice::OnSysDynamicDeviceInit()
{
BYTE x;
*pVal=0;
pMyInt=new MouseInt();
if(pMyInt == NULL)
T.Trace(TraceAlways,"invalid handle!\n");
//////////////////////////////////////////////////////////
//////////driver monitor out put here,that hook failed///
          if(!pMyInt->hook())
T.Trace(TraceAlways,"hook failed!\n");
//////////////////////////////////////////////////////////
           if(pMyInt&&pMyInt->hook())
{
_outp(0x2f9,1);
_outp(0x2fa,0);
_outp(0x2fc,0x0b);
pMyInt->physicalUnmask();
}
return TRUE;
}

BOOL MouseDevice::OnSysDynamicDeviceExit()
{
_outp(0x2f9,0);
_outp(0x2fc,0);
T.Trace(TraceAlways,"interrupt Closed\n");
delete pMyInt;
return TRUE;
}
MouseInt::MouseInt()
:VHardwareInt(IRQ_3,1,0,0)
{
}

VOID MouseInt::OnHardwareInt()
{
(*pVal)++;
T.Trace(TraceAlways, "interrupt detected!\n");
_inp(0x2fa);
_inp(0x2fd);
_inp(0x2f8);
sendPhysicalEOI();
}

用softice调一下，看看是不是hook()没有成功

如果你确实装了鼠标，请用VSharedHardwareInt

这个例子是鼠标中断，但是是对Com端口来进行的。我以前测试也不行！

我说的是Serial 鼠标啊
如果你的com口上没有设备,哪里来的中断源?
但是如果你的com口上有serial鼠标的话,那么,已经有一个vxd
在管理这个中断了,所以我觉得应该用VSharedHardwareInt
我学这个的时候,想都没想就用VSharedHardwareInt了
此外,据我所知,如果鼠标中断来了以后,读取某一个串口端口
(具体哪个我忘了)会清除中断,所以,我觉得不应该在你自己的vxd
中那样做,应该把那些_inp去掉,并在OnSharedHardwareInt中
return FALSE,不要尝试进行任何操作,比如sendPhysicalEOI
等等

我以前在nt下想截获seiral鼠标中断,但结果是,虽然能够截获
但是这时鼠标不能动作了,可能就是这个原因

如果是WIN9X 那应没问题，看一下有没有中断源，即发信息的，如果没有就接一个鼠标。