The Pspasswd utlitiy, which comes as part of the Sysinternals PsTools kit, can be used to reset the local administrator password on machines locally or remotely. Obviously, this comes in handy when you’re not sure of the local administrator password on a domain joined machine.
Resetting the local administrator account on a single machine:
pspasswd \\server.contoso.com administrator "passwordGoesHere"
You can also specify a list of computer names in a text file to change the password on multiple machines. The example below assumes computerlist.txt contains a list of computer names, one per line:
pspasswd \\@computerlist.txt administrator "passwordGoesHere"