volume shadow copy system being installed on XP Pro standalone?
If not, what are some suitable free alternatives?
As far as I can tell, it is part of XP Professional anyway (it comes with the ntbackup.exe).
I found an overview of its as part of the Microsoft Windows XP Professional overview on MSDN, which I would also take as indication that it is built into XP Pro.
The Wikipedia article about Shadow Copy says "The Volume Snapshot Service was first added to Microsoft Windows in Windows XP"