So first grab the copy from Logiqx.com (left, Datutil).
Its a commandline tool that converts your dats between various formats, mainly CMP/RC.
Enter the commandline in your OS, point it to the directory containing the tool and the dat file that needs to be converted.
See the documentation for the correct options (should be none for CMP -> RC 2.0) , enter it like
E:>datutil.exe my_dat_file.dat
After that you should see a new file in the RC 2.0 format (can easy be checked by opening the file in an texteditor (compare the 'Style' with the old file and see the difference).