Windows authentication - Prompted for credentials - SSO

Hello,

I've the following problem: I have an intranet .net website on IIS, configured to useonly Windows Authentication and when I try to access my website using IE (8 to 10),it prompts me for my credentials, although I'm logged on the network with a domain account. So I enter my credentials and I have access to the site (no need to enter my credentials anymore even if I clear my browser cache or if I close and reopen my browser). BUT, if I make a restart on my IIS Server Manager, I have to enter my credentials again (I don't want this behavior).

What I want is that once logged on my computer (with a valid user account of my AD), I directly access my websitewithout having to enter any username/password thanks to the Windows Authentication on IIS, and even if I make a restart on my IIS Server or something else (so, just a classical SSO, hein?, SSO should not ever prompt for credentials, right?).

In more details:

• I use IIS 7.5 with the following configurations:
  • Authentication on my Webiste configured with: Windows Authentication Enabled / All others autentication Disabled (I'm using SSO)
  • My website use an AppPool configure in Integrated Mode and with .NET framework 4.0. The app pool identity is set toNetwork Service.
  • I access my webiste through the url: http://myMachineName:85

• My ASP.NET website is configured as follow:
  • In the web.config, <authentication mode="Windows"/>

• My architecture is as follow:
  • The network service account has full control on my website directory
  • Windows Server 2008 R2 Standard SP1 with IIS 7.5 and my website. The server is on the local domain.
  • I try to access the website using 
    • a client computer belonging to the same domain
    • I'm logged on the client computer with a user belonging to my AD. It's a classic domain user
  • There is no firewall activated
  • There is no proxy used

What I've already tried:

• My website start page is recognized as "Local intranet | Protected Mode: On" (in the page property)
• IE (8 to 10) is configured to "Automatic logon with current user name and password"
• Alaready tried to add my domain as a trusted Zone or Trusted site on Local Intranet in IE (8 to 10)

I need some help because I can not figure out why IE asks me for credentials. For me, all is well configured. I really don't understand what the problem is. If someone has an idea...

Thanks you for your answers!