We've been burned at my work by old word and word perfect documents from early 90's refusing to render properly in new versions of office. I think they tried about three recent versions of office before they gave up and resorted to scanning in hard copies as PDF's to recover some documents.
Access databases are also notorious for this problem. A lot of business apps were written with Access in the mid 90's and it has now become too expensive/time consuming to migrate them off of a dead technology. In business world stuff tends to run far longer than softawre developers consider. Hell COBOL and PL/1 stuff runs in some places still.