Heres how to keep your computer lean and mean. Avoid installing software just to try it out. Innumerable installs and uninstalls clog your machine - eventually. If you must try out software then do so on another machine to decide if its a keeper. Check what programs are on your startup menu. Some may not be necessary but before you uncheck make sure. You can do without skype and messenger starting up each time you boot but leave system files alone.
If you are at your wits end with a computer that just crawls along - transfer all your docs to an external hard drive and reinstall your operating system. I have friends who do this as a matter of course every six months. It works! Voila! Clipping speeds once more!