Using the management console, check where the archive logs are kept. Note: Do NOT EVER delete the redo log files, those are needed by the system. If you are unsure, google "oracle archive logs" and read up on the subject.
When sure, locate the archive log files older than N days by saying for instance
"find . -mtime +30 | grep archive/ | xargs ls"
Check the files again, and if you are 100% sure, substitute ls with rm and run the search again.
Now you have to tell RMAN that those archive logs are gone:
"/oracle/app/oracle/product/9.2.0/bin/rman target sys"
password: (xxxxxxxx)
"crosscheck archivelog all;"
"delete expired archivelog all;"