I recentley found this post from Santhosh Sivarajan’s blog which gives you an easy way to identify and delete inactive or stale computers in an Active Directory enviroment. Using the dsquery command you can easliy find all of the computers in the directory that have not been logged into in a given time interval or disabled.
The following command will return all computers that have been inactive or stale for 2 weeks:
dsquery computer -inactive 2
The Following command will return all disabled computer account information.
dsquery computer -disabled
You can combine this output with the dsrm command to delete these objects from Active Directory.
dsquery computer -inactive 2 | dsrm -noprompt dsquery computer -disabled | dsrm -noprompt