how do i automatically assigned a custom usergroup upon registration
 

I created a 'probation' usergroup that can't send PMs, and I want them to 'graduate' to a normal registered member status after 25 posts. Could someone walk me through how to do that?

Thanks a ton. :)

i would set it up in reverse.. have the default registered users as the probation group and promote them into something else with more permission. much easier then hacking up your forum to get the same end result.

good suggestion.

I've done that, now is there a way to 'run' it so that all members who have more than 25 posts get moved to the new group I've created?

If you have set-up a promotion then they will all get moved next time the cron job runs (which is normally once an hour). You could, of course, run it manually.