Office 2003

I have the following Excel code snippet in a macro
which did run fine until I had to do a major reinstallation.
Now it hangs on the fs= bit with the error message
Compile Error. Can't find the Project or Library.
I believe I'm missing a Reference under Tools/Reference,
but have no idea which one(s).
Can anyone help?

Set fs = CreateObject("Scripting.FileSystemObject")

donwb