If you open FS9.cfg, there should be a section somewhere with a header:
[OldModules]
If not, create that inside the file, and add the given line under it, then save the cfg. I am sorry to say, that I do not know if it works or not, because I stand absolutely clueless at this problem.
FS9.cfg is somewhere under C:\Documents and settings\***USER***\Application data\Microsoft\FS9