Thanks! Now theirs a few things to go through! In your moodle files, you will have an Auth folder, within this folder you should have a folder called ldap, in the folder should be some files named nlmsso.php etc.. Assuming you have ldap working I would say you have these!
The next step is to change the authentication method that IIS is using. the standards are Anonymous Authentication and ASP.NET Impersonation! these two wont work for auto login through ldap. the correct method you need to have is Windows Authentication! once this is installed on IIS you then need to enable it, and disable the other two. You will also need to go into the properties of Windows Authentication and select the NTLM provider and move it to the top, above negotiate.
This step can be done on the tab for the default web site, and also on the auth folder in your moodle dir!
The final step in to get this working is to go into your moodle site administration page, go to your plugins and look at the settings for your ldap server. somewhere near the bottom of your settings you will find a section called NTLM SSO in here you change the settings for auto login;
Enable: set to yes
Subnet: set to the IP ranges your pc's use e.g. 172.16.1, 172.16.2....
MS IE fast path: set to yes
Authentication type: set to NTLM
Remote username format: set this to your domain and username e.g.
%domain%\%username%
This gives the domain name and username a variable, meaning that it will sign you in with the domain and username of the specific user that has logged on.
If all of these settings are done correctly then auto login to the moodle front page will work when in your network, outside of the network they will have to type there username and password that they use in school.
If you have any issues, please reply and I will go through this with you in more detail, I can also attach some guides to follow that will help also.