Logon denied

My friend brought his computer home from work. He was a part of his domain there. Yet, in order to access files on my personal computer, we changed his domain to the workgroup MSHOME. When we had to reset, it brought up his login. It had his last username-the one he used to logon at work- and but his password would not work. So, he’s locked out of his account, he can’t log in at all. Any ideas?

*EDIT* Guest account is also disabled.