Database's characterset is set during the database creation, it doesn't depend on any init parameter.

You can find what your current database parameter is by querying the NLS_DATABASE_PARAMETER system view.

I belive you'll find your 10g database has some kind of unicode characterset, while your 8i database probably has US7ACII or some other characterset that is not capable of accepting characzer "Ñ".

Under some circumstances, you can change your database characterset, but if those circumstances are not met you'll have no other choice but to rebuild your whole database with different characterset.