Hi... back up exec during install can install a msde version of SQL2000.
On one of our 2003 servers i need to install a program that will install SQL 2005 express edtion for it to use... I believe u can run the two side by side but as two seperate instances of SQL. But you can also upgrade a existing sql 2000 instance ie the backup exec one to the SQL2005 fomat......... IF i do this wiill backup exec 9.1 still function ???