I've tried setting up mod_auth_sspi, but have not managed to get SSO working.
I then realised that this may be because my stack (Uniform Server 8.2) doesn't include Tomcat. I read somewhere some instructions for using mod_auth_sspi that suggested Tomcat was required, but I haven't seen it in the official documentation for mod_auth_sspi nor the Drupal install guide for mod_auth_sspi that I had been working on.
Ideally I'd rather avoid Tomcat as it has a tendency to be a security flaw.
The other option would be to use NTLM, but I don't think NTLM works with Apache on Windows?