The Microsoft ISATAP device Inter Site Automatic Tunneling Address Protocol is used to help enterprises transition to an IPv6 infrastructure. The driver is built in Windows.
On a Windows Vista-based computer or on a Windows Server 2008-based computer, the Microsoft ISATAP adapter appears with a yellow exclamation mark next to it in Device Manager, and you also receive an error message
http://support.microsoft.com/kb/932520/en-us
IPv6 network adapters are reinstalled when network connectivity is restored on a computer that is running Windows Vista or Windows Server 2008