'Before using this, please update at LEAST the first two lines, and review the others to see what tokens you can use.
'Provide the source and destination files for token replacement.
'If they are the same, the tokens will be replaced and the file will be overwritten

Const Source = "D:\Windows\Panther\unattend.xml"
Const Destination = "D:\Windows\Panther\unattend.xml"

'Provide a list of token names and values to replace
Dim tokens
Set tokens = New TokenList
tokens.AddToken "SERIALNUM", "%SERIALNUM%"

'Main program

'Constants that do not change
Const ForReading = 1
Const ForWriting = 2

'Declare Variables for use in token replacement.
Dim fileSource, fileDestination, objFSO, strContent

'Create a file system object
Set objFSO = WScript.CreateObject("Scripting.FileSystemObject")

'Open the source file and read it's content
Set fileSource = objFSO.OpenTextFile(Source, ForReading, False)
strContent = fileSource.ReadAll()
fileSource.Close

'str replacement 
'read thru each entry in the array and substitute in the tokenized file
For i = 0 To tokens.Size
    strContent = Replace(strContent, "%" & tokens.Name(i) & "%" , tokens.Value(i))
Next    

'Open Destination file and write updated content to it
Set fileDestination = objFSO.OpenTextFile(Destination, ForWriting, True)
fileDestination.Write(strContent)
fileDestination.Close



'TokenList Class   
Const ARRAY_INCREMENT_SIZE = 10
Class TokenList
                Public aData
                Public iCount
                Public iSize
                
                Private Sub Class_Initialize()
                                iCount = 0
                                iSize = ARRAY_INCREMENT_SIZE
                                ReDim aData(1, iSize)
                End Sub
                
                Public Function AddToken(Name, Value)
                                If iCount > iSize Then
                                                iSize = iSize + ARRAY_INCREMENT_SIZE
                                                ReDim Preserve aData(1, iSize)
                                End If
                                aData(0, iCount) = Name
                                aData(1, iCount) = Value
                                iCount = iCount + 1
                End Function
                
                Public Property Get Name(iPos)
                                If iPos < 0 OR iPos >= iCount Then Exit Property 'Invalid range
                                Name = aData(0, iPos)
                End Property
                
                Public Property Get Value(iPos)
                                If iPos < 0 OR iPos >= iCount Then Exit Property 'Invalid range
                                Value = aData(1, iPos)
                End Property
                
                Public Property Get Size()
                        Size = iCount
                
                End Property
                
                
End Class