What is the best all-in-one PC optimization program?

Price for the most part is not matter, I just want all my computers to run at their full potential. My Windows XP computer has been sluggish recently and I want a easy to use program that will cover all aspects of my computer and speed it up that works very well. I have tried several before and none really helped. Please let me know the name of anything you think would be good or a link to their site. Thank you.