Is it possible to migrate from Informix SQL to Informix for Windows NT?
Yes. Informix for Windows NT is now on version 7.31. This has the exact same functionality as 7.31 for UNIX. You won't be able to use the byte-level dumps/restores of tbunload or onunload, but you should be able to export the database using either dbexport/dbimport or flat-file ASCII unloads by using the SQL statement
UNLOAD to tablename.unl SELECT * from tablename
LOAD from tablename.unl INSERT into tablename;