SetFilePointerEx doesn't seek my memory flash, why is this?

See more:

C#

API

Hello again...I've a problems trying to move the pointer forward.. I'm trying to read my flash memory as array of bytes... Using SetFilePointerEx API function I've already did it, but, the problems is that it always read begening at 0 byte, I can't begin with offset of 512 bytes for example... why is this.....Note: it works pretty well seeking a file like .txt file. Some help.. please....I really need some help..

My code:

SafeFileHandle ptrFile = CreateFile("\\\\.\\u:", DesiredAccess.GENERIC_READ | DesiredAccess.GENERIC_WRITE, ShareMode.FILE_SHARE_READ_AND_WRITE, IntPtr.Zero, CreationDisposition.OPEN_EXISTING, FlagsAndAttributes.FILE_ATTRIBUTE_NORMAL, IntPtr.Zero);

        byte[] buffer = new byte[512];

        uint readed = 0;
        try
        {
           bool retor = SetFilePointerEx(ptrFile, 512, IntPtr.Zero,      MoveMethod.FILE_BEGIN);
        }
        catch (Exception)
        {
           throw new Win32Exception(Marshal.GetLastWin32Error());
        }

        bool b = ReadFile(ptrFile, buffer,512 , out readed, IntPtr.Zero);