Find inactive users in AD

You can use dsquery( http://technet.microsoft.com/en-us/library/cc732952(WS.10).aspx ) to get a list eg. to find all inactive user accounts for 8 weeks

dsquery user -inactive 8 -limit 0

Otherwise, you can also try this active directory cleanup tool (http://www.lepide.com/active-directory-cleaner/) to generate the comprehensive report on all inactive users accounts that have not logged on within last x number of days and shows the list of inactive users.