Cleaning stale users and computers in AD can be a pain, but this little utility makes it a breeze to identify and delete old users and computers.

ADTidy

Identify and clean up inactive user and computer accounts in your Active Directory domain
Search your Active Directory domain for user/computer accounts that are no longer in use by filtering based on last logon time, DNS record timestamp, and much more. You can then perform a number of actions on the accounts that were found - such as moving them to another OU, disabling them, setting a random password, removing them from all groups, and much more.

Features 
Report on both user and computer accounts 
Search entire domain or select a specific OU 
Multi-domain friendly - specify any domain and optionally use alternate credentials to connect to it 
Get account last logon information from all DCs or select specific DCs (using either lastLogon attribute or lastLogonTimeStamp attribute) 
Choose to only find accounts that have not logged on for a specified number of days 
Confirm whether or not computer accounts are still active by using the Ping test and DNS record timestamp check
Powerful filtering capabilities let you filter results accounts based on name, group membership, expiration date, LDAP attribute, and more
Export report results to CSV or Excel XLSX file
Save report settings to file so that you can reload them whenever you want  or share them with colleagues
Option to reverse actions that were previously performed (Standard Edition only)
Command line support and Automated Rules allow for automation of account clean up tasks (Standard Edition only)

For any accounts that are found in the report, you can perform one or more of the following actions:
Disable 
Delete 
Move To Another OU 
Set Description 
Set Expiration Date 
Add To Group 
Remove From Group 
Remove From All Groups 
Hide From Exchange Address Lists 
Delete home drive 
Clear LDAP Attribute Value 
Run External Script
Set Random Password 
Disable OWA 
Set Password To Never Expire 

You can also combine any of these actions into an Action Sequence to speed up common clean up tasks such as disabling accounts and moving them to another OU at the same time. Action sequences can be performed manually on any selected accounts, or by automated rules and command line scripts.

Screenshots (Standard edition) - Click to enlarge

Main Window	Configuring a Filter
Available Actions	Performing Actions
Reversing Actions	Configuring Visible Columns
New Automated Rule - General	New Automated Rule - Account Selection
New Automated Rule - Actions	Automated Rules List
Configuring Action Sequence	Creating Command Line Config File