TaskKeyHook.h

////////////////////////////////////////////////////////////////
// MSDN Magazine — September 2002
// If this code works, it was written by Paul DiLascia.
// If not, I don't know who wrote it.
// Compiles with Visual Studio 6.0 and Visual Studio .NET on Windows XP.
//
#define DLLIMPORT __declspec(dllimport)

DLLIMPORT BOOL DisableTaskKeys(BOOL bEnable, BOOL bBeep);
DLLIMPORT BOOL AreTaskKeysDisabled();

TaskKeyHook.cpp

////////////////////////////////////////////////////////////////
// MSDN Magazine — September 2002
// If this code works, it was written by Paul DiLascia.
// If not, I don't know who wrote it.
// Compiles with Visual Studio 6.0 and Visual Studio .NET on Windows XP.
//
// This file implements the low-level keyboard hook that traps the task 
// keys.
//
#define _WIN32_WINNT 0x0500 // for KBDLLHOOKSTRUCT
#include <afxwin.h>         // MFC core and standard components

#define DLLEXPORT __declspec(dllexport)

//////////////////
// App (DLL) object
//
class CTaskKeyHookDll : public CWinApp {
public:
   CTaskKeyHookDll()  { }
   ~CTaskKeyHookDll() { }
} MyDll;

////////////////
// The section is SHARED among all instances of this DLL.
// A low-level keyboard hook is always a system-wide hook.
// 
#pragma data_seg (".mydata")
HHOOK g_hHookKbdLL = NULL; // hook handle
BOOL  g_bBeep = FALSE;     // beep on illegal key
#pragma data_seg ()
#pragma comment(linker, "/SECTION:.mydata,RWS") // tell linker: make it 
                                                // shared

/////////////////
// Low-level keyboard hook:
// Trap task-switching keys by returning without passing along.
//
LRESULT CALLBACK MyTaskKeyHookLL(int nCode, WPARAM wp, LPARAM lp)
{
   KBDLLHOOKSTRUCT *pkh = (KBDLLHOOKSTRUCT *) lp;

   if (nCode==HC_ACTION) {
      BOOL bCtrlKeyDown =
         GetAsyncKeyState(VK_CONTROL)>>((sizeof(SHORT) * 8) - 1);

      if ((pkh->vkCode==VK_ESCAPE && bCtrlKeyDown) || // Ctrl+Esc
          // Alt+TAB
          (pkh->vkCode==VK_TAB && pkh->flags & LLKHF_ALTDOWN) ||   
          // Alt+Esc
          (pkh->vkCode==VK_ESCAPE && pkh->flags & LLKHF_ALTDOWN)|| 
          (pkh->vkCode==VK_LWIN || pkh->vkCode==VK_RWIN)) { // Start Menu
         if (g_bBeep && (wp==WM_SYSKEYDOWN||wp==WM_KEYDOWN))
            MessageBeep(0); // only beep on downstroke if requested
         return 1; // gobble it: go directly to jail, do not pass go
      }
   }
   return CallNextHookEx(g_hHookKbdLL, nCode, wp, lp);
}

//////////////////
// Are task keys disabled—ie, is hook installed?
// Note: This assumes there's no other hook that does the same thing!
//
DLLEXPORT BOOL AreTaskKeysDisabled()
{
   return g_hHookKbdLL != NULL;
}

//////////////////
// Disable task keys: install low-level kbd hook.
// Return whether currently disabled or not.
//
DLLEXPORT BOOL DisableTaskKeys(BOOL bDisable, BOOL bBeep)
{
   if (bDisable) {
      if (!g_hHookKbdLL) {
         g_hHookKbdLL = SetWindowsHookEx(WH_KEYBOARD_LL,
            MyTaskKeyHookLL, MyDll.m_hInstance, 0);
      }

   } else if (g_hHookKbdLL != NULL) {
      UnhookWindowsHookEx(g_hHookKbdLL);
      g_hHookKbdLL = NULL;
   }
   g_bBeep = bBeep;

   return AreTaskKeysDisabled();
}