Pinvoke call for getting the windows serial number

ManagementObjectSearcher mos = new ManagementObjectSearcher("Select * From Win32_OperatingSystem");
 // ...
 // Select number from managementobject mo["SerialNumber"]

#include <WINIOCTL.H>
extern "C" __declspec(dllimport)
BOOL KernelIoControl( DWORD dwIoControlCode, LPVOID lpInBuf, DWORD nInBufSize, LPVOID lpOutBuf, DWORD nOutBufSize, LPDWORD lpBytesReturned );
#define IOCTL_HAL_GET_DEVICEID CTL_CODE(FILE_DEVICE_HAL, 21, METHOD_BUFFERED, FILE_ANY_ACCESS)

CString GetSerialNumberFromKernelIoControl() {
    DWORD dwOutBytes;
    const int nBuffSize = 4096;
    byte arrOutBuff[nBuffSize];
    BOOL bRes = ::KernelIoControl(IOCTL_HAL_GET_DEVICEID, 0, 0, arrOutBuff, nBuffSize, &dwOutBytes);
    if (bRes) { CString strDeviceInfo; for (unsigned int i = 0; i<dwOutBytes; i++) {
    	CString strNextChar; strNextChar.Format(TEXT("%02X"), arrOutBuff[i]); strDeviceInfo += strNextChar;
    }
    CString strDeviceId = strDeviceInfo.Mid(40,2) + strDeviceInfo.Mid(45,9) + strDeviceInfo.Mid(70,6);
    return strDeviceId;
    } else {
    	return _T("");
    }
}

[DllImport("coredll.dll")]
    public static extern bool KernelIoControl(long dwIoControlCode, IntPtr lpInBuff, long dwInBuffSize, IntPtr lpOutBuff, long dwOutBuffSize, IntPtr lpBytesReturned);

if(Environment.OSVersion.Platform == PlatformID.WinCE) { ... }