I set this up on my sons PC it drives him MAD it turns the PC off each evening and restricts his login
shutdown.bat contains
c:\windows\system32\shutdown.exe -f -s
And i run this on his PC in a batch file to set it up
net user "Rupert" /time:M,6:00-21:00;T,6:00-21:00;W,6:00-20:00;Th,6:00-21:00;F,6:00-23:00;Sa,6:00-23:00;Su,6:00-20:00
at \\rupertpcxp 20:00 /every:m,t,th "c:\windows\shutdown.bat"
at \\rupertpcxp 20:00 /every:su,w "c:\windows\shutdown.bat"
at \\rupertpcxp 22:00 /every:F,SA "c:\windows\shutdown.bat"
works on vista and XP, I think I made the schedule service start with an admin account