http://www.fileheap.com/software/auto_shutdown.html
here is a list of programs that will shut down your computer at certain times. Some are free, some are not.
Would your child honor the shut down? or would he simply restart and keep playing?
They do sell child lock/child timers for xp
http://wareseeker.com/Home-Education...zip/3b76ca599f This program is $19.95. PLEASE read the whole thing before you decide to buy ANY program. There are many free things out there if you search.
I hope you get some sleep.