From time to time you might need to clean up the Active Directory from computer accounts which are no longer active. Computers that has been reinstalled, replaced with new ones, old VMs. In many of those case you’ll might just end up with active directory full of computer objects that are obsolete. In fact those old unused accounts are called stale accounts.
AD Tidy tool
The creator of this tool is Chris Wright from the UK. There is free version and paid version of this tool. This tool is about 4 Megs in size and enables you to do many things concerning housekeeping of Active Directory. After running a report tool which brings results, you can select the desired records and do some actions, like disabling, moving, addint/removing to/from groups etc. You can also set expiration data on objects. The tool uses powerful filtering options and can do a lot of actions. You can also build your own action sequences or export pie charts.
--> please see the rest on Vladan's blog : http://www.vladan.fr/how-to-find-inactive-computer-accounts-in-active-directory/