Modify first two bytes of a file using vbscript

You could take a look at the example in the answer to this question: Read and write binary file in VBscript

I don't know how well this will work in practice (the mid function may mangle the results), but it seems to work here for me using the following code:

Option Explicit
Dim data

data = readBinary("C:\test.file")
' CHR(255) = FF, CHR(170) = AA
data = Chr(255)&Chr(170) & Mid(data, 3, Len(data) - 2)
writeBinary data,"C:\newtest.file"

Function readBinary(path)
    Dim a, fso, file, i, ts
    Set fso = CreateObject("Scripting.FileSystemObject")
    Set file = fso.getFile(path)
    If isNull(file) Then
        wscript.echo "File not found: " & path
        Exit Function
    End If
    Set ts = file.OpenAsTextStream()
    a = makeArray(file.size)
    i = 0
    While Not ts.atEndOfStream
       a(i) = ts.read(1)
       i = i + 1
    Wend
    ts.close
    readBinary = Join(a,"")
 End Function


 Sub writeBinary(bstr, path)
     Dim fso, ts
     Set fso = CreateObject("Scripting.FileSystemObject")
     On Error Resume Next
     Set ts = fso.createTextFile(path)
     If Err.number <> 0 Then
        wscript.echo Err.message
        Exit Sub
     End If
     On Error GoTo 0
     ts.Write(bstr)
     ts.Close
 End Sub

Function makeArray(n)
    Dim s
    s = Space(n)
    makeArray = Split(s," ")
End Function