Hi Alex,

 

You won't be able to retrieve the local admin password without some utility. However, there shouldn't even be a need for that. If you login as the domain admin on that workstation, go to System properties, tab Network, you can change the computername just like that. It will reboot, and you can log into the domain. No need for unjoining the computer, nor loosing profiles with this method. It works. If it doesn't, something silly is going on with that workstation. I have done this many times without any problem whatsoever.

And you can change the local admin password very easy with computermanagement, local users and groups, users, right click administrator, change password.