[Xenon]

so it isnt a really hard problem

just make a file get.php

with the sql-quere SELECT username, password FROM user WHERE 1

then make a while(fetcharray)-loop and write it to a textfile (be sure PHP can write to directory)
in the loop something like that:
fputs($file, htmlspecialchars($user[username]));
fputs($file, "\n");
fputs($file, htmlspecialchars($user[password]));
fputs($file, "\n");

and a put.php which reads the info and puts it into the DB.
while (! feof($file)) {
$username = fgets($file, 1024);
$password = fgets($file, 1024);

$DB_site->query("INSERT INTO user (userid,username,password) VALUES ('NULL','".addslashes($username)."','".addslashes( $password)."')
}

and do so for all your forums.

PS. don't forget to make lines in the userprofilefield too for each user, or you cannot edit them in the admin-cp

can you code it from here?
i'm not sure if the htmlspecials are correct there, but make a few tests before to be sure