I assume you want to reset the local Administrator password on all client computers joined to the domain. You cannot "remove" it. I would not do this in a logon or startup script, but rather reset all of the passwords in bulk using a script you run from your workstation. I have an example VBScript program for this linked here:
The program reads computer names from a text file, logs all activity, and saves a file of computer names where the password was not set (probably because the computer was off line). Each computer needs to be authenticated to the domain (started), it doesn't matter if anyone is logged on. You can run the program repeatedly with the missing computer file until the password has been changed on all computers. The advantage with this method is that you know when the password has been changed on all computers.
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