In Autoit werden Strings mit dem "&" zeichen verbunden.
Code:
$var = "OS: " & @OSVersion & "..."
Der 2. Parameter des FileOpen befehls steht für den Modus.
Code:
 0 = Read mode
  1 = Write mode (append to end of file)
  2 = Write mode (erase previous contents)
  4 = Read raw mode
  8 = Create directory structure if it doesn't exist (See Remarks).
  16 = Force binary(byte) reading and writing mode with FileRead and FileWrite
  32 = Use Unicode UTF16 Little Endian mode when writing text with FileWrite and FileWriteLine (default is ANSI)
  64 = Use Unicode UTF16 Big Endian mode when writing text with FileWrite and FileWriteLine (default is ANSI)
  128 = Use Unicode UTF8 when writing text with FileWrite and FileWriteLine (default is ANSI)
Und du willst ja eine Datei schreiben und nicht auslesen. Also kann 0 nicht stimmen.