The best way I've found of handling this is to use a standard 24hour plug in timer to switch the power to the computer off and on at appriate times. That way you don't have to fund an idle computer from your electricity bill! Assuming you need it, get one that handles daylight saving (summer time) time correctly.
1. Make the scheduler close the machine down 5 minutes or so before the power will be cut off
2. Ensure the power saving options in the BIOS and in Windows are set to reboot on power fail. This ensures the machine starts up when the power is restored.
Finally, check the clock on the timer once or twice a year - they can drift by a few seconds a week.