注册表的简单操作

void CSLtestDlg::OnButton3() 
{
// TODO: Add your control notification handler code here
//读取注册表中的值
HKEY hKey;
//DWORD dwType;
TCHAR szNameServer[256]; //LPBYTE
DWORD dwDataSize=256; //LPDWORD
DWORD dwType;


LONG retval=RegOpenKeyEx(HKEY_LOCAL_MACHINE,"SYSTEM\\CurrentControlSet\\services\\umbus",0,KEY_QUERY_VALUE,&hKey);
if(retval==ERROR_SUCCESS) //若调用成功
{
RegQueryValueEx(hKey,_T("DisplayName"),NULL,&dwType,(LPBYTE)szNameServer,&dwDataSize); //获取值
}


AfxMessageBox((CString)szNameServer);

//创建键值
LONG retva=RegCreateKeyEx(HKEY_LOCAL_MACHINE,"SYSTEM\\CurrentControlSet\\services\\gogo",0,
NULL, REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS,NULL, &hKey,NULL);
if(retval==ERROR_SUCCESS)
{
if(RegSetValueEx(hKey,_T("HAPPY"),0,dwType,NULL,NULL)==ERROR_SUCCESS) //写入数据
{
AfxMessageBox("写入成功");
}
else
{
AfxMessageBox("写入失败");
}
}

RegCloseKey(hKey);

}

出现了写入失败，也不知道怎么回事？？