CreateFile() Works in Windows XP but fails in Windows 7 return Handle Invalid

While trying to create a handler using CreateFile(), even when executing the application as administrator, I get the following error message: ‘The system could not find the specified file. (Exception from HRESULT: 0x80070002)":Nothing.’

Here is a sample of the code being used for this task:

Private Enum EFileAccess As System.Int32
        GENERIC_WRITE = &H40000000
End Enum

Friend Enum EFileShare        
    FILE_SHARE_READ = &H1
    FILE_SHARE_WRITE = &H2
End Enum

Friend Enum ECreationDisposition        
    OPEN_EXISTING = 3
End Enum

Friend Enum EFileAttributes
   FILE_FLAG_NO_BUFFERING = &H20000000
End Enum

<DllImport("kernel32.dll", SetLastError:=True, CharSet:=System.Runtime.InteropServices.CharSet.Auto)> _
    Private Shared Function CreateFile(ByVal lpFileName As String, _
                                ByVal dwDesiredAccess As EFileAccess, _
                                ByVal dwShareMode As EFileShare, _
                                ByVal lpSecurityAttributes As IntPtr, _
                                ByVal dwCreationDisposition As ECreationDisposition, _
                                ByVal dwFlagsAndAttributes As EFileAttributes, _
                                ByVal hTemplateFile As IntPtr) As Microsoft.Win32.SafeHandles.SafeFileHandle
    End Function

The path points to a matrix printer in a Windows Server 2003.

handle = CreateFile(\\brbhzpc001154\Epson_2180,
                                EFileAccess.GENERIC_WRITE,
                                EFileShare.FILE_SHARE_READ Or EFileShare.FILE_SHARE_WRITE,
                                IntPtr.Zero,
                                ECreationDisposition.OPEN_EXISTING,
                                EFileAttributes.FILE_FLAG_NO_BUFFERING,
                                IntPtr.Zero)

This application, when compiled works without any error in Windows XP, but when trying to execute in Windows 7, the error described above always happens.

There are solutions here suggesting that on Win7 changing OPEN_EXISTING to OPEN_ALWAYS will make it work on Win7, but with no explanation why.