1) You might have an alarm set. Try this. From the "main menu" of the iPod, select Extras. Select Alarms.

That's on my iPod classic.

On the 2G Nano, it's main menu, then extras, then Clock. I then select the clock or time zone, then Alarm Clock.

I've had that "spontaneously" appear before. Very annoying if it's set to 3 AM!

2) I'm not going to get into this one. It does sound like permissions since Y and Z can access iDVD. I'd go with wingnut's suggestion to look at the Apple discussion forums or Google.

I don't think the problem is getting Y and Z access to the photos of X (which is fairly easy to do) as much as figuring out why iDVD won't start for user X.

Thanks for the Take Control suggestions, dtsm. I definitely know some people who can use them!