Cannot Disable Terminal Services in Services MSC

I'm running WXP Pro SP3 with all wanted updates. Although I could not Stop
the service,I disabled (originally in Automatic) Terminal Services in the
Services MSC. After reboot, Terminal Services was still running & was in
Manual (Windows apparently switched it from Disabled to Manual). I was able
to disable the service in the Registry, but I'm curious as to why I can't
accomplish this now as I've always done before. Has perhaps a recent
Microsoft security update caused this change in behavior? Anyone know?
--
Joe Davis