Outlook Express – End of file has been r

I have a friend that is receive the following error when trying to open Outlook Express on her mac. Now I know NOTHING about Macs. The error is “End of file has been reached” Any ideas? Also how is mailed and the address book stored on a mac.Would they still be there? I know in windows you can search for ???.pab or ????.pst.

Is there any hope in recovering her mail and address book if it is infact gone?