Upgrading from vBulletin 2 
Note:
This page applies soley to upgrades from vBulletin 2 to vBulletin 3. If you are already running a version of vBulletin 3 you may skip this section.
Having successfully uploaded all the new vBulletin files to your web server, you will need to make a note of the existing values in the vBulletin 2 admin/config.php file and apply them to the new vBulletin 3 includes/config.php.new file as described here.

There will now be a little maintenance to be done on the files stored on your web server in order to clean up vBulletin 2 files and directories that are no longer used in vBulletin 3.

With the remote forums directory showing in your FTP client, you should delete the following files and directories:

Having completed this deletion process, you can run the vBulletin 2 to vBulletin 3 upgrade script.

Please note that depending upon the size of your existing database and the speed of your web server, running the initial phase of the upgrade process to convert your vBulletin 2 database to be compatible with vBulletin 3 may take a long time. A million-post database may take several hours to upgrade.
Patrick Van der Veken 20th Apr 2005, 11:03am
Following files should also be deleted from an old vb2 installation:

* private2.php
* sendtofriend.php