Not sure what the cause of this is but you should try running a search for all the DBF files on your system (these are the files that contain all your email and folders etc). If you recognise any of the names then you need to look where they are stored. Then go into OE and choose Tools, Options, Maintenance Tab, Store Folder - this is the folder that all your DBF files will be stored, If you dont recognise it, change it to the location of the stored DBF files when you ran the search.
Regards
Maz