From my prespective it depends upon how you back up your system and do your
work flow.
I keep all my files and project that are continuing WIP in my MY Documents
tree. Stuff that is deemed at a production state I move to the main areas on
the system, e.g. for the web go on in to inetpub/wwwroot, programs go into
program files, etc.
This allows a page backup scheme MyDocuments are done daily, rest of the
hard drive weekly, and full drive image at the end of the month.
