So, I gather that this is a windows server since you mention .exe's and 'domain controller.' So, if you are the Administrator, then why can't you just reset their passwords? You don't need a user's password to reset it to something else if you are the administrator of the server that those user accounts live on. So, you could reset all their passwords, and then send them the new passwords; then, you could set it so that each user must change their password the next time they log in.

Or am I just missing something big here?