how do I clear passwd history of a user without compromising the audit trail for security?
in a nutshell, user abc wants to re-use his passwd ( he is not savvy with computers )
Warning: this is my opinion.
You can't - you are talking about changing your security for a user because of his/her issues with remembering a new password. I'm sure the savvy hacker can act just as dumb as a non-savvy user to get by your security measures if you start making exceptions for folks that can't make up a new password.
Give him/her a pad of paper and pencil and take away the computer.
(END RANT)
Please post the OS and version and any 3rd party security software you might be using - then an appropriate answer can hopefully be given to allow this.
AIX 5.1/5.2
no vendor software is installed, just using the standard smitty settings for each user (must change 3 chars/nums)
This is not a safe request. Why would you cater to this user's inablility to remember a password?
Is it the CEO? 
I am not an AIX guy. But poking around the man pages, I found chuser. It looks like:
chuser histsize=0 username
might do it.