Checking the last logon date of computer

I am the administrator of a NT 4.0 Domain of about 3500 workstations. We have a product (BindView) to help with delegation of management of users and computers to local managers. This works great, however, if I look in Server Manager I notice that there are about 4000 computer accounts when we only have 3500 machines. This means that there are about 500 computer accounts that are no longer being used. What I am looking for is a way to tell which accounts those are so they can be removed. Maybe use a method that will display the last time a computer account has been used to logon to the Domain. Any help would be appreciated.