Please delete old thread which has sensitive info

It is not the general policy to edit or delete forum posts. When a post is made and people contribute answers to an issue, that then becomes part of the community resource for others to benefit from. Editing or deleting posts removes this added value. In extreme circumstances, the moderation team might be persuaded to remove sensitive information but. generally, your best course of action is not to publish anything that you wouldn’t want to be public.

http://codex.wordpress.org/Forum_Welcome#Deleting_.2F_Editing_Posts