I find Diskeeper to be a great tool for longitivity. It makes my PC feel as if I had installed Windows on it yesterday.

It is a shame that people have to go to third parties in order to keep their computers running at full efficency. Software to keep computers running at full efficency is really something I expected to find intergraded with Windows (while being easily accesible, used and configured so you don't have to do it manually), from Microsoft.