In IE you can set the checkbox “Enable Integrated Windows Authentication” (Internet Options, Advanced Tab, below the heading Security)

Internet Explorer version 6 and 7 will use Integrated Windows Authentication whether you have the checkbox enabled or disabled. The big difference lies in the type of authentication which is kerberos or NTLM. If the option is checked IE will first try Kerberos and then will fallback to NTLM, if the option is unchecked it will just use NTLM. So Microsoft labeled the option wrong, it should say Negotiate Windows Authentication or so. Checking or unchecking this option just sets the registry key “HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\EnableNegotiate” to 1 or 0.