Problem in Conversion of CDS/ISIS data into MARC21

Dear All,

I have been using CDS/ISIS software (Dos version) for my Library for many years. Most of the fields (including subfields like multiple authors- ^aSimpson^bAlan%^aBuxton^bAndrew) are in CCF but some fields tag are locally given which are not similar to CCF. I have now more than 25000 data in the database. I would like to convert my whole data (by making MST.ISO) into MARC21 format. How can I do that?
(1) I tried to convert it by using ‘marcedit’ by Terry Reese. When I open MarcEdit and use CDS/ISIS.iso => Marc Translation from Add-ins option and give Input File name from my exported data from CDS/ISIS Software (MST.ISO) and give name of my Output data (which is converted into – ‘MST.marc’, the file shows the data contains ‘0’ Byte. That means no data has been converted (from MST.ISO to MST.marc using marcedit software).
I tried several times but the results became same. Would anybody please suggest me something for solving this problem?
(2) I also used to convert the same CDS/ISIS data (MST.ISO) into Access by using ‘IsisConvert’ . But while converting the program shows that the process has been completed  but only data of two fileds have come as output in ‘Access’  out of several fields in original file in CDS/ISIS. I have tried several times but the result are same. Would anybody kindly suggest me the easiest step by step process of converting CDS/ISIS data Into MARC21 Format or in Access?

With regards,