Steve forgot the password on his all-in-one Windows 10 machine. Leo says that can be a serious problem in Windows 10. But since Steve used his Microsoft account to log in, he can change the Microsoft password and he should be able to make it work. Microsoft also has a utility called MSDaRT, which has a feature called Locksmith Wizard that will reset his Windows 10 password. Third party utilities include PC Unlocker.
Here's an article on Six Ways to Reset a Forgotten Windows Password from top-password.com.
If he doesn't care about the data, he can also just do a reset and it will erase the entire hard drive and reinstall Windows.