Has anyone came across a problem whereby the data files just become empty. The OS file structure and contents appear perfectly.

the My Documents, the My Picture folder etc. just become empty for no apparent reason

The usual programs Getdataback etc cannot find them either.

Where do I start in such a recovery?

(user does not report any evidence of foul play, sabotage etc as the system, a Dell XPS laptop was in their possession all the time)

OS = Vista Premium
HDD = WD Scorpio.

Fat32 by a chance?

Vista File System is ntfs, but files aren't in the expected locations
Documents and settings folder is just a place holder.
The real files are in user folder which may or maynot be hidden.
Then of course if chkdsk was run, files may be in found folders.