hello sir,u need a tool named Implex but it will coz some serious problems
vb 4.0.3? I though vb 4.0.2 is the latest. Anyway I'd also advise staying away from VB for a while. IPB 3.1 is about to be released and looks fantasitic. You should wait for vBulletin 4 to become a bit more stable and have the problems fixed and by then IPB 3.1 will be out and you won't want to move.
EDIT: oh ya 4.0.3 came out yesterday. Cool I'll have a look and see what's fixed
IPB is the most secure script,Its not very easy to hack
Stay with IPB,I am using it..its pretty cool B-)