I don't have 8.0 anymore (only 8.1.6 and 8.1.7) :D
Anyway, the best way is deleting all *.ora (SQLNET.ORA, TNSNAMES.ORA, LISTENER.ORA)
Delete means backup and then delete.
And enter to the Net8 Assistant (Not the Easy)
If that doesn't work, check the nmi*.log to see what's happening.