SAP: deleted users [when/who]?
Actions that are done to a user profile, be that creation, modification or deletion are tracked in a table USH04.
The field PROFS will reflect each of the actions referencing the following characters:
A: add
M: modify
D: delete
Simply enter the user you are interested in and see what has occured over the year.
SAP: Check the Passwords of Standard Users in All Clients
A quick way to check the status of all the standard users in your SAP system is to run a program RSUSR003.