My personal strategy for backing up my data from Windows is to exlusively use the user folders (Documents, Downloads etc.) and just copy them to another harddrive when I need/want to reinstall Windows. Also most applications save their data to the hidden Folder AppData so this one has to be copied too.
Bigger trouble is to backup the windows registry, for which I haven’t found a good solution yet, since I was not in need to back it up.
A nice alternative to transfer windows now comes from c’t . Their might be a usecase in the future…