Application needs write access to C:\windows\

So I think the software developers who make our accounting application are not following best practices with one of their add-ins.

They have a spell-checking tool that needs to be installed to C:\Windows\System. Contained in the tool is a dictionary file. Users are expected to add items to this dictionary file, and therefore would need write access to this directory.

Am I wrong in assuming that this is impossible given our users do not have local admin rights? Isn't it necessary for the users to have write access to c:\ and c:\Windows parent directories in order for this to work?

All in all this seems like a very bad idea on their part. Am I wrong?