NewEra, OEM vs. ANSI - Problem

Hello everybody, by migrating database applications developed in a DOS enviroment (INFORMIX 4.01 DC - Informix ONLINE 5.xx on a SUN Server) to the NewEra (partially to VIEW POINT PRO) envirement occured the problem of displaying special characters like the german Umlaute (', ', ') or french characters with diacritica (', ', ', ', etc.). For most rows in the DB have been inserted under the old conditions (oem) the display of the above characters in the windows envirement shows a 'defecit'. e.g. der G'RTNER (DOS client) der G_RTNER (Windows client) where the underscore stands for some not printable character. Unloading the DB converting those files may be one solution. But I wonder wether there may not exist another strategy. I would deeply appriciate a suggestions to get rid of this problem. Thanks Peter