Yes, you can

To disable the Control Panel in Windows XP:Click Start and click Run.Type gpedit.msc and click OK.Within the Group Policy Editor, expand the following: User Configuration | Administrative Settings | Control Panel.In the details pane, double click Prohibit access to the Control Panel.Click Enabled and click OK.With this setting enabled, users will be unable to start the Control Panel or run any Control

I agree with the earlier poster, that messing with the control panel requires some "time out" from computer time. Its MUCH easier to give each child a name/user account of their own, with their own pass word. They can make the wallpaper whatever they want, and drag the icons around to include the programs they want to use. It wont interere with the others users, or the taste of the rest of the house. MANDATORY that mom keeps a copy of the passwords, and follows up on where this child has been while on it.

Hope that helps.

btw, mess with your computer at YOUR own risk. What I have shown you is an easy to use method, but is normally only used by advanced users. Make sure you create a back up or restore point before trying this so you can restore back to the way it was if it messes up.