[Xenon]

you have to alte table thread add one extrafield called prefix varchar(10) (should be enough )

then you have to modify at least 2 files:
newthread.php (add an input field for Prefix into the newthread template and don't forget to save it in DB newthread.php)

forumdisplay.php (add $thread[prefix] in forumdisplaythreadlistbit(forgot the correct name ) template and change the query to also get thread.prefix out of the database