Data files – can they just disappear?

I have a user on a shared XP workstation who has suddenly lost all of her data files in a fairly complex folder structure. The folders are all in place, the applications are there – just every data file she had has suddenly disappeared! The files are word, excel, powerpoint and various graphics files. The other user of the system has similar files that are all still in place. I have checked the files haven’t been hidden, that there is no virus or spyware on the system and the recycle bin has just a few files (some of which pre-date the loss of the data). Has anyone any idea what else could be the cause of this?

We encourage our users to save onto the network drives as these are backed up regularly… and of course she hadn’t backed up her files on the C: drive!

Many thanks

David