Use the Windows 2000 resource kit utility cusmgr.exe. This tool allows you to remotely change passwords using a preprepared file. Simply create a file with as many of the following statements as you need:
cusrmgr.exe -u Administrator -m \name_of_computer -P newadministratorpassword
One computer per line. Make sure the text file is saved with a .bat extension and then when it is run, the local administrator password will be changed on each computer. DO not store the file (I wouldn't want any available record of passwords for local admin acounts to be around). Here's additional information from KB article 272530.
This was first published in April 2004