This Zen Cart Add-on will allow you to log into your admin, search for an email address for a customer, then click and re-set the password to one of your choosing.
This DOES NOT email the customer the new password. You either need to tell them verbally or email it to them yourself.
NOTE: If you have any type of Checkout Without An Account module installed, if the customer chose to use COWOA, they did not actually "create an account" so you cannot reset a password in this case.
Works with versions 1.3.9, 1.5.0, 1.5.3, 1.5.4
NOTE: Not needed with Zen Cart Version 1.5.5 because it is now a part of that code.