table prefix issue in installation

hi Michal,

I already installed the 1.03 server version with certain table prefix, but when upgraded to 1.04 version, I forgot to use the same prefix, hence in database there are two sets of same kind of tables with prefix and without prefix, so

1. please advise how to identify and remove unnecessary tables:
2. in particular version upgrade in future, if I used the same prefix used in 1.03, is there any chance for table overwritten,

regards,
suminda,