I have installed SharePoint 2010 Beta on a Windows 2008 R2 server. central administrations -> Review problems and solutions: All Reports page was showing warning like : “The Security Token Service is not available”.
1) Verify the sequences of your installation as below:
- Install hot fixes [Windows6.0-KB971831-x64]
- Install SharePoint prerequisites from SharePoint setup splash screen [ This should ask for machine restart ]
- Install SharePoint 2010 beta.
2) If your sequence matches with (1) then you might have not restarted your machine after above installation. So restart your machine and check again the error/warning message stated above should now disappeared.