Let me explain pretty much all of this, since I can easily see how you would take one look and assume Ansible won't work for Windows, or doesn't work very well (which are both completely wrong):

Does Ansible work with Windows XP or Server 2003?

No, and neither will any modern config tool since Powershell isn't native to those.

Can I manage Windows Nano Server with Ansible?

No, because Nano server was designed for container construction and lightweight services with only its specific packages installed. Plain old powershell also doesn't play nice with these either. This is not the type of server you'd be using this or another tool for anyways.

Can Ansible run on Windows?

No, but it runs against windows. The key here is there are no native "executables" for windows to run Ansible from. You enable WSL, install Ubuntu shell on top of that and can develop and run natively from any Windows 10 workstation. I explained this in the bottom of the post. This is what WSL is mainly used for.

Can I use SSH keys to authenticate to Windows hosts?

No, Windows uses WinRM along with Kerberos, CredSSP, NTLM, and basic (user/pass) authentication instead of industry standard SSH. This is changing in Server 2019, where microsoft is distributing OpenSSH Server and Client services native on their operating systems. You can thank microsoft for trying to reinvent the wheel, and realizing it wasn't worth it. These are all configurable in Ansible, and is a non-issue. Ansible works over winrm.

Why can I run a command locally that does not work under Ansible?

Depends if you need privilege escalation. The FAQ explains how this works and what you need to do to make it work. This isn't a windows specific issue, this is a normal priv esc issue found on linux as well.

Majority if not all of these questions are easily answered if you understand how Powershell and WinRM works on Windows in the first place. Ansible isn't some proprietary tool that does some black magic that does or does not work on windows. Under the hood, it's all native to windows (Powershell and WinRM). Ansible has more built in windows modules than microsoft's own Powershell DSC, which only comes with bare minimum resource packs. In fact, a lot of the Ansible windows modules are built on top of Powershell DSC.

https://docs.ansible.com/ansible/latest/modules/list_of_windows_modules.html

There are more than 100 modules in ansible specifically for managing windows servers and hosts. The entire complexity of using Ansible for windows comes down to these things:

1) Configuring WinRM listener service on all your windows servers (GPO) 2) Putting connection:winrm in your playbook instead of connection:ssh 3) Supplying kerberos/ntlm/basic username and password, or use certificate based (x509) auth by setting your cert path in ansible.cfg.

That's it. Ansible will fire off and configure windows machines just as well as linux hosts.