Running additional scripts during registration

[Disasterpiece]

you can check the registration php script and watch out for fetch_hook calls, because these are the hook locations you can add a plugin to.

First you follow the script code to the point where you have all the vars/information you need, then you look for the next available hook name.
Then navigate to the "add plugin" link in your admincp, enter the hook location and you can add your code using the local vars from the code where the hook gets called.

You can use the vbulletin database interface from $vbulletin->db. For information about the API, check the vbulletin api documentation or look for the classes_core.php file in includes dir.