來電鈴聲的設置在注冊表中的HKEY_CURRENT_USER\\ControlPanel\\Sounds\\RingTone0\\Script下的值，就是所要播放的鈴聲文件。查看Windows Mobile下的注冊表，用VS2005中Visual Studio Remote Tools->Remote Registry Editor工具就可以，不須其他的軟件。
我們可以在電話來了后根據號碼播放不同的鈴聲，然后在通話結束再將鈴聲恢復。下面是通過MAPI來實現
1.判斷來電號碼
VOID CALLBACK LineCallback(DWORD hDevice, DWORD dwMsg, DWORD dwCallbackInstance, DWORD dwParam1, DWORD dwParam2, DWORD dwParam3)
{
 switch(dwMsg)
    {
    case LINE_CALLINFO://1L呼叫信息
  {
   switch(dwParam1)
   {
   case LINECALLINFOSTATE_CALLERID://0x00008000
    {
     LINECALLINFO *lpCallInfo;
     lpCallInfo = (LINECALLINFO *)malloc(sizeof(LINECALLINFO)+1000);
     memset(lpCallInfo, 0, sizeof(LINECALLINFO)+1000);
     lpCallInfo->dwTotalSize = sizeof(LINECALLINFO)+1000;
     while (1)
     {
      lineGetCallInfo( (HCALL)hDevice, lpCallInfo);
      if (lpCallInfo->dwTotalSize < lpCallInfo->dwNeededSize)
       lpCallInfo = (LINECALLINFO *)realloc(lpCallInfo,lpCallInfo->dwNeededSize);
      else
       break;
     }
     
     lstrcpy(szPhoneNumber,(LPTSTR)((LPSTR)((DWORD)lpCallInfo+(DWORD)lpCallInfo->dwCallerIDOffset)));
     free(lpCallInfo);
     // szPhoneNumber  ---- 呼入的電話號碼
     //char strPhoneNumber[30 + 1] = {0};
   //在這里根據號碼來設置鈴聲
   
                 
}
  break;
 case LINE_LINEDEVSTATE:
  break;
 case LINE_APPNEWCALL:  //有呼叫進來23L
  break;
 case LINE_REPLY:
  break;
 case LINE_CALLSTATE:  //呼叫狀態2
  {
  case LINECALLSTATE_DISCONNECTED://掛機
   {
         RedoReg();
   }
   break;
  }
  break;
 }
}
DWORD InitializeTAPI(void)
{
 ReadReg();//讀系統中默認的鈴聲設置
     //在啟動中加入初始化
 if ( lineInitialize( &LineApp, g_hInst, (LINECALLBACK)LineCallback, g_szAppWndClass, &LineHandleCount) == 0)
 {
  LineHandles = new HLINE[LineHandleCount];
  for(DWORD i = 0; i < LineHandleCount; i++)
  {
   int rc;
   DWORD ver;
   LINEEXTENSIONID extensionID;
   
   if ( lineNegotiateAPIVersion( LineApp, i, 0x00010003, 0x00020000, &ver, &extensionID) == 0)
   {
    rc = lineOpen( LineApp,
     i,
     &LineHandles[i],
     ver,
     0,
     (DWORD)0,
     LINECALLPRIVILEGE_MONITOR|LINECALLPRIVILEGE_OWNER,
     LINEMEDIAMODE_INTERACTIVEVOICE,
     NULL);
            }
        }
 }
 
 return 0;
}
2，讀取并保存系統鈴聲
void ReadReg(void)
{
 HKEY hKey = NULL;
    HKEY hSubKey = NULL;
 LRESULT SS;
 SS = RegOpenKeyEx(HKEY_CURRENT_USER ,L"\\ControlPanel\\Sounds\\RingTone0", 0,0,&hKey);
 if(ERROR_SUCCESS != SS)//打開注冊表失敗
  RegCloseKey (hKey);

 DWORD    lpType = 1; 
 DWORD   lpcbData = 80;
 SS = RegQueryValueEx(hKey ,L"Script", (LPDWORD)NULL,NULL,(BYTE*)lpData,&lpcbData);
 DWORD Result = GetLastError();
 if(ERROR_SUCCESS != SS)//讀鍵值失敗
  RegCloseKey (hKey);
}
3，更改鈴聲設置
void WriteReg(void)
{
 LRESULT lr;
 HRESULT hr = E_FAIL;
 HKEY hKey = NULL;
 DWORD dwDisposition;
 TCHAR wszValue[60] = L"a";
 
 lr = RegCreateKeyEx(HKEY_CURRENT_USER, TEXT("\\ControlPanel\\Sounds\\RingTone0"),
  0, NULL, 0, 0, NULL,
  &hKey, &dwDisposition);
 if (lr != ERROR_SUCCESS)
  RegCloseKey(hKey);
 
 lr = RegSetValueEx(hKey, L"Script", 0, REG_SZ, (LPBYTE) wszValue, (lstrlen(wszValue) + 1) * sizeof(TCHAR));
 if (lr != ERROR_SUCCESS)
  RegCloseKey(hKey);
 
 RegCloseKey(hKey);
 hKey = NULL;
}

4.通話結束，釋放資源并恢復系統鈴聲
void ReleaseLine(void)
{
 RedoReg();

 for ( DWORD i=0; i<LineHandleCount; i++ )
 {
  lineClose( LineHandles[ i ] );
 }
void ReadReg(void)
{
 HKEY hKey = NULL;
    HKEY hSubKey = NULL;
 LRESULT SS;
 SS = RegOpenKeyEx(HKEY_CURRENT_USER ,L"\\ControlPanel\\Sounds\\RingTone0", 0,0,&hKey);
 if(ERROR_SUCCESS != SS)//打開注冊表失敗
  RegCloseKey (hKey);

 DWORD    lpType = 1; 
 DWORD   lpcbData = 80;
 SS = RegQueryValueEx(hKey ,L"Script", (LPDWORD)NULL,NULL,(BYTE*)lpData,&lpcbData);
 DWORD Result = GetLastError();
 if(ERROR_SUCCESS != SS)//讀鍵值失敗
  RegCloseKey (hKey);
}
 delete[] LineHandles;
 lineShutdown( LineApp );

}