Sceduling an automated task is like pulling teeth w/ my Computer!

OK, here's the thing. I followed These Steps and went ahead and setup a scheduled shutdown time using Windows shutdown.exe program. My computer is a Windows XP Service pack 3.

I followed the directions to a 'T' with the only difference being the time

to shut down and still no dice! It just so happened that i fell asleep but the computer didn't. I don't know what's happening. Maybe it's a setting that i changed some time ago that may be affecting my comp now and preventing the automatic scheduled shutdown from functioning. I don't know

Please Help!