Is there software I can buy to increase computer performance?

I want to buy a program off the shelf, not download, that will improve the performance of my computer. It is very slow to boot, and when I am trying to download a video or even open a website it takes a very long time of freezes. There or times when I click on a desktop icon and nothing happens. What I am looking for is a program that will scan my computer and look for hidden programs or extra programs that will remove the programs that are not needed. I do not play any games on it. I have System Mechanic 6 on it and I have Norton 360. Some other programs that are suppose to increase performance but do not. Windows XP. I downloadd Service Pack or Patch 3 for XP and everything stopped working until I deleted it.