The error=5 typically means "Access is denied" - for some reason your system does not allow plug-in registration. Do you run your installer "as administrator" ?
As a experiment, please start command line prompt "as administrator", then 'cd' to "c:\NXP\FreeMASTER 3.2\FreeMASTER" and run register.bat.
Send a screenshot of the console output.
Thanks,
Michal