software will be of no use if you want it to turn your computer on, from being in a totally off state. for this, you can buy timers that fit into the electrical sockets, so you can set the computer to come on at a certain time, etc.
you could however put your computer into hibernation mode, and i'm sure there's software somewhere that will bring your computer out of it at what time you specify.
try looking at http://www.downloads.com