resetting pm messages

the other night some members went on my forum delated stuff as one was a moderator,i noticed they have pm heaps of people telling them to come to there new forum,is there anyway i can reset the pm messages so all messages to all members are delated and start new from scratch,i have pm not in use at the moment on the forum but would like to allow it for members

I made a 2 days backup of your forum, so all PM's have been deleted in this scale of time

If you want a further backup, please tell!

so if a back up was done say to the 24th of september could it then be updated again to the 4th of oct without losing to much info ,or would i lose info on the forum and need to hand back this up

when you backup to a certain date, you lose all data from after that date, like if it never existed