Killing off your programs will not speed up your computer, it will only free up drive space.
The single biggest cause of computers slowing down (that I have seen) is programs that start with Windows and then disappear from the tray. They are fully loaded and are doing nothing beneficial for you. If they didn't start with Windows you would have that much more free memory to use and Windows wouldn't be wasting time polling them to see if you are trying to bring them up from inactivity.
Microsoft in it's ever-challenged wisdom, has a "feature" to hide those programs from you by default. It is called "Hide inactive icons" and "Group similar taskbar buttons." This makes people go out and buy faster and faster machines they can ill-afford to do, thinking they need a faster machine than they have.
Turn off "Start with Windows" in all programs you don't use all the time. Start those programs when you are actually going to use them.
Enable all tray items to be visible so you can see what is loaded at any time and don't allow grouping of taskbar buttons. Then you can see what gets loaded with Windows and take measures to not start them until you need them.
Start>Settings>Control Panel>Taskbar and Start menu;
Uncheck "Hide inactive icons"
Uncheck "Group similar taskbar buttons"
Now look at the tray is see what's running that you don't need, go to options in those programs and de-select "Start with Windows" or whatever their exact words may be.
Your computer will boot faster and run faster with un-needed programs no longer starting with Windows.