Power managment.

So somewhere, somehow my computer lost its power managment options. I'm running XP media center addition. I did a fresh install about a month ago and sometime since then most of the power managment option disappeared. The only things that I can still control are turn off monitor and turn off hard disks. I don't want to have to reinstall just for that so if someone has any ideas I'd really appreciate it. It's just nice for me to let the computer hibernate or turn off after so long because I frequently get distracted and leave it for hours on end. I know it doesn't use a lot of power but anything that helps, well helps. So I don't know if there's a way to fix it or if there are any other options. Any and all help is welcome.

Run Windows setup from within Windows and select "Repair Install". It should repair any damaged files without going through the whole installation process and all your files and programs will be left untouched.