off hand i would say, you could write a script that goes through all of the computers in the domain and pings them. if the ping fails, write the computer name to a text file.
you could also gather a list of the computers in the domain and compare it to the DNS records for the domain.
either way, you could end up with some false positives if a computer still has a dns record but that IP is being used by another computer.
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Josh
CCNA, MCSE 2003(in progress)