Unless you know the a valid username and password for the Laptop local accounts you will be reinstalling windows. Usually Administrator is the username but its anyone's guess at the password. I am pretty sure there is no way back.
You could see if you can get in safe mode and when it comes to login page press Ctrl = Alt + Del twice this may show you the local accounts on the machine and give you a chance. Maybe even use the username with no password.
No it needs to be the Password and Username setup on the PC not the ones that used to log in to the domain. Maybe you could whack a Windows disk in and then boot from that choose recovery console followed by a system restore back to a day before you changed it off the domain to get it back to how it was.