As Kenneth stated, if you get into your system BIOS at bootup, normally by pressing or holding down a function key during POST, you should find Power Management or Auto Power On settings. Once enabled, you should also be able to select a time for everyday, or weekdays only. Obviously, these features depend on your BIOS version. This works on my Dell Optiplex 960 as well as my optiplex GX270 (2003 model).