ok, be careful not the customer id but the license of your vb3.
(better to check in /forumdir/index.php at the top)
in vb3 it's in /forumdir/includes/config.php at the bottom. prefix bb
in pp it was in config-inc.php, now (above 4.8.?) it's in the pp settings table id 172.
Normally you won't need to reinstall, dunno what things you wanna change