I already used nLite to disable automatic updates and others, but I still have to remove the tray notifications regarding automatic updates and security center.

What registry entries do I need to add?

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center]

"AutoUpdateDisableNotify"=dword:00000001

"UacDisableNotify"=dword:00000001

"InternetSettingsDisableNotify"=dword:00000001

This will disable warnings for automatic updates, uac and the firewall being turned off. UNFORTUNATELY, the uac disable only works on vista business and ultimate...I have not found a solution for this, other than NOT turning off UAC.

As for the antivirus, there is a key called antivirusoverride (google it and you'll find the key) but this registry entry is protected with permissions so a standard regedit will not work.