In 3.8.6 version, we found a few serious bugs to run NONMEM with fit4NM.
When you remove fit4NM from your system, all information about fit4NM in registry will be deleted from this version, which is to fix path problems in configuration.
Unfortunately, we found that OpenOffice did not work for fit4NM. So, currently fit4NM is highly dependent of MS excel. Moreover, excel should be installed in the default pathway when installed. This is because fit4NM uses Excel parser.