为什么我无法打开驱动程序

我已经确信驱动程序已经被系统加载到了内存，下面的代码执行的结果就是
显示ERROR。
是因为带波浪线的地方的问题，还是Guid不匹配的原因？

#define HELLO_CLASS_GUID \\
{0xff646f80,0x8def,0x11d2,{0x94,0x49,0x0,0x10,0x5a,0x07,0x5f,0x6d}}

GUID HelloClassGuid = HELLO_CLASS_GUID;
......
hHello = OpenByInterface( &HelloClassGuid,0,&Error);
if (hHello == INVALID_HANDLE_VALUE)
{
 printf(\"ERROR opening device: (%0x) returned from CreateFile\\n\",    GetLastError());
 exit(1);
}
......

inf中的信息

Class=NewDeviceClass
ClassGUID={ff646f80-8def-11d2-9449-00105a075f6b}
......

[Hellowdm_AddService]
DisplayName    = %SvcDesc%
ServiceType    = 1                  ; SERVICE_KERNEL_DRIVER
StartType      = 3                  ; SERVICE_DEMAND_START
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ErrorControl   = 1                  ; SERVICE_ERROR_NORMAL
ServiceBinary  = %10%\\System32\\Drivers\\Hellowdm.sys

OpenByInterface用的是驱动用IoRegisterDeviceInterface注册的Interface名，不是GUID