Well, in vBulletin the user table holds
Now, if this table is shared between various installation with the methode posted above (which ist of course possible) there will be a lot of problems.
For example the post counter:
You make 1 post in board 1, but as board 2 uses the same table it will also show 1 post .
guys you got my idea wrong..
I'm not talking about sharing the user table between two forums..
what I meant is to modify register.php or any other neccassry files to add any registered user with his information to the other forum database..so the user won't have to register twice..and uses his same password / username in both forum..and then (posts - cookies - new options...) sure will be different..
so if the user registered in one of these forums.. he will have the same login information in the other forum..ofcourse until he changes one of them..